Downloaded 2,852 times
![6
4. NhËp v l−u d÷ liÖu (Use, input and and save)
Më tÖp sè liÖu ®ang cã:
TÖp sè liÖu Stata cã thÓ ®−îc më b»ng lùa chän Open trªn thùc ®¬n File; hoÆc nót Open (use) trªn
thanh c«ng cô tool bar.
NÕu file sè liÖu cã dung l−îng lín th× chóng ta ph¶i thiÕt lËp bé nhí cÇn dïng cho Stata b»ng lÖnh:
set memory #[k|m]
VÝ dô:
set mem 32m
set mem 32000k
NhËp sè liÖu
Cã mét sè c¸ch ®Ó nhËp sè liÖu tõ b n phÝm v o bé nhí cña Stata.
- Sö dông cöa sæ Stata editor ®Ó nhËp sè liÖu. HoÆc tõ cöa sæ command, gâ lÖnh edit. Sau ®ã
nhËp sè liÖu theo kiÓu biÓu b¶ng trong cöa sæ n y.](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-6-320.jpg)
![8
Ch−¬ng II: Khai th¸c d÷ liÖu
1. CÊu tróc lÖnh trong Stata (Stata command syntax)
CÊu tróc c¬ b¶n cña mét lÖnh trong Stata nh− sau:
[by danh s¸ch biÕn:] Có ph¸p lÖnh [danh s¸ch biÕn] [biÓu thøc] [®iÒu kiÖn] [ph¹m vi] [quyÒn sè]
[, tuú chän]
Trong phÇn H−íng dÉn s− dông (Help) cña Stata, có ph¸p lÖnh tr×nh b y b»ng tiÕng Anh nh− sau:
[by varlist:] command [varlist] [=exp] [if exp] [in range] [weight] [, options]
Trong ®ã dÊu ngoÆc vu«ng ký hiÖu c¸c tuú chän.
Chó ý:
- C¸c c©u lÖnh Stata ®−îc viÕt b»ng ch÷ th−êng.
- §èi víi tªn biÕn, Stata ph©n biÖt ch÷ viÕt th−êng víi ch÷ viÕt hoa. VÝ dô, trong cïng mét tÖp sè
liÖu, biÕn “Ho_ten” v biÕn “ho_ten” l 2 biÕn kh¸c nhau.
- C¸c tuú chän ®−îc ký hiÖu trong dÊu ngoÆc vu«ng [ ]. C¸c tuú chän n y cã thÓ cã hoÆc kh«ng
trong c©u lÖnh. C¸c tham sè b¾t buéc (tªn biÕn) ®−îc ®Æt trong dÊu ngoÆc < >. C¸c c©u lÖnh sÏ
kh«ng thùc hiÖn ®−îc nÕu c¸c tham sè b¾t buéc n y kh«ng ®−îc khai b¸o.
- Mét sè lÖnh Stata cho phÐp viÕt t¾t. VÝ dô lÖnh summarize cã thÓ viÕt t¾t l sum. Trong cuèn
t i liÖu n y phÇn g¹ch ch©n d−íi có ph¸p cña c©u lÖnh l có ph¸p “viÕt t¾t” cña c©u lÖnh ®ã.
- C¸c vÝ dô trong cuèn t i liÖu n y sö dông sè liÖu §iÒu tra Møc sèng d©n c− n¨m 1998 do Tæng
côc Thèng kª tiÕn h nh. Trong ®ã TÖp chi tiªu tæng hîp Hhexp98n.dta th−êng xuyªn ®−îc sö
dông.
by danh s¸ch biÕn (by varlist): Stata sÏ thùc hiÖn c©u lÖnh víi theo tõng gi¸ trÞ ®−îc chØ ra bëi danh
s¸ch biÕn. BiÕn ®−îc chØ ra bëi danh s¸ch biÕn ®−îc yªu cÇu s½p xÕp tr−íc khi thùc hiÖn lÖnh.
VÝ dô:
. sort sex
. by sex: sum rlpcex1
-> sex = 1
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
rlpcex1 | 4375 2980.906 2430.648 357.318 45801.71
-> sex = 2
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
rlpcex1 | 1624 3748.368 3231.241 376.9805 30624.77](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-8-320.jpg)
![12
C¸c h m sè (function)
H m sè th−êng ®−îc dïng trong biÓu thøc (exp) cña c©u lÖnh Stata. NÕu coi Y l mét h m sè cña f(X1,
X2,…, Xn) th× lÖnh vÒ h m sè trong Stata sÏ tÝnh gi¸ trÞ cña Y nÕu cho c¸c gi¸ trÞ cña Xi. Stata cã 8 lo¹i
h m sè:
Mathematical functions
Statistical functions
Random numbers
String functions
Special functions
Date functions
Time-series functions
Matrix functions
C¸c h m to¸n häc
H m thèng kª
H m cho sè ngÉu nhiªn
H m liªn quan ®Õn dÉy ký tù
H m ®Æc biÖt
H m ng y th¸ng
H m chuçi thêi gian
H m ma trËn
VÝ dô:
gen absx=abs(x)
gen log_exp=log(rlpcex1)
C¸c ký hiÖu cô thÓ vÒ c¸c h m sè n y cã thÓ xem ë môc help functions.
3. M« t¶ d÷ liÖu (Data reporting)
3.1. Xo¸ bé nhí cña Stata
Có ph¸p:
clear
LÖnh n y xo¸ c¸c d÷ liÖu trong bé nhí cña Stata, b¾t ®Çu cho mét file l m viÖc míi.
3.2. H−íng dÉn sö dông lÖnh Stata
Có ph¸p:
help <C©u lÖnh Stata>
LÖnh n y hiÓn thÞ h−íng dÉn sö dông c¸c lÖnh Stata, lÖnh Stata cÇn ph¶i ®−îc gâ ®Çy ®ñ v chÝnh x¸c.
VÝ dô:
. help sum
help for sum not found
try help contents or search sum
. help summarize
-----------------------------------------------------------------------------------------
help for summarize (manual: [R] summarize)
-----------------------------------------------------------------------------------------
Summary statistics](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-12-320.jpg)
![13
….
Chó ý:
Chóng ta cã thÓ t×m h−íng dÉn sö dông theo tõ kho¸ b»ng lÖnh search. LÖnh search cã thÓ ®−îc thùc
hiÖn b»ng tuú chän Search ë thùc ®¬n help.
Chóng ta còng cã thÓ dïng cöa sæ lÖnh b»ng menu bar
3.3. M« t¶ d÷ liÖu
Có ph¸p:
describe [danh s¸ch biÕn]
LÖnh n y hiÓn thÞ th«ng tin chung nh− tªn biÕn, ®Þnh d¹ng, nh n biÕn cña c¸c biÕn ®−îc liÖt kª bëi
danh s¸ch biÕn cña file sè liÖu ®ang më. NÕu nh− kh«ng cã biÕn n o ®−îc chØ ra th× lÖnh describe sÏ
hiÖn thÞ th«ng tin cña tÊt c¶ c¸c biÕn.
VÝ dô:
. des househol year month vlssmphs
storage display value
variable name type format label variable label
-------------------------------------------------------------------
------------
househol long %12.0g household code](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-13-320.jpg)
![14
year float %9.0g Year of interview
month float %9.0g Month of interview
vlssmphs byte %8.0g 1 if vlss, 2 if mphs
source
3.4. HiÓn thÞ gi¸ trÞ cña c¸c biÕn
Có ph¸p:
list [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel]
LÖnh n y hiÓn thÞ gi¸ trÞ cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn. Tuú chän nolable cho phÐp hiÓn
thÞ gi¸ trÞ sè chø kh«ng ph¶i l gi¸ trÞ g¸n nh n.
VÝ dô:
. list househol farm in 1/5
househol farm
1. 36307 farm
2. 28002 farm
3. 36017 farm
4. 32418 non farm
5. 15215 non farm
. list househol farm in 1/5, nolabel
househol farm
1. 36307 1
2. 28002 1
3. 36017 1
4. 32418 0
5. 15215 0
3.5. Söa ch÷a, xem sè liÖu
Có ph¸p:
edit [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel]
browse [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel]
LÖnh edit n y më cöa sæ Data editor ®Ó ng−êi sö dông söa ch÷a, nhËp sè liÖu. Tuú chän nolable cho
phÐp hiÓn thÞ gi¸ trÞ sè chø kh«ng ph¶i l gi¸ trÞ g¸n nh n. LÖnh n y cã thÓ ®−îc chän tõ tuú chän Data
editor trong thanh thùc ®¬n Windows.
LÖnh browse gièng lÖnh edit nh−ng kh«ng cho phÐp söa ch÷a sè liÖu.
3.6. §Õm quan s¸t
Có ph¸p:
count [®iÒu kiÖn] [ph¹m vi]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-14-320.jpg)
![15
LÖnh n y ®Õm sè quan s¸t ®−îc chØ ra bëi ®iÒu kiÖn (exp) v ph¹m vi (range). NÕu ®iÒu kiÖn (exp) v
ph¹m vi (range) kh«ng ®−îc chØ ra th× sÏ hiÖn thÞ sè quan s¸t cña tÖp sè liÖu.
VÝ dô:
. count
5999
. count if reg7==1
859
. count if reg7==1 & urban98==1
187
. count if reg7==1 & urban98==0
672
3.7. Thèng kª c¬ b¶n
Có ph¸p:
summarize [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, detail]
LÖnh n y tÝnh to¸n v hiÓn thÞ nh÷ng thèng kª c¬ b¶n cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn.
Tuú chän detail cho phÐp hiÓn thÞ thªm mét sè thèng kª nh− ®é nhän, ®é lÖnh v c¸c gi¸ trÞ cña thËp vÞ
ph©n.
VÝ dô:
. sum rlpcex1
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
rlpcex1 | 5999 3188.667 2692.567 357.318 45801.71
. sum rlpcex1, detail
comp.M&Reg price adj.pc tot exp
-------------------------------------------------------------
Percentiles Smallest
1% 682.9575 357.318
5% 1012.433 366.2792
10% 1238.088 376.9805 Obs 5999
25% 1671.054 381.3502 Sum of Wgt. 5999
50% 2397.042 Mean 3188.667
Largest Std. Dev. 2692.567
75% 3711.917 26944.64
90% 5940.803 30624.77 Variance 7249918
95% 8045.32 31066.5 Skewness 3.791027
99% 14163.04 45801.71 Kurtosis 29.21398](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-15-320.jpg)
![16
3.8. HiÓn thÞ th«ng tin chung vÒ biÕn
Có ph¸p:
inspect [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi]
LÖnh n y m« t¶ vÒ sè liÖu cña c¸c biÕn kiÓu sè. Nã ®−a ra th«ng tin vÒ sè ©m, d−¬ng, sè nguyªn, gi¸ trÞ
thiÕu (missing) cña gi¸ trÞ cña biÕn.
VÝ dô:
. gen x=invnorm(uniform())
. inspect x
x: Number of Observations
---- Non-
Total Integers Integers
| # Negative 2964 - 2964
| # Zero - - -
| # Positive 3035 - 3035
| # ----- ----- -----
| # # # Total 5999 - 5999
| . # # # . Missing -
+---------------------- -----
-3.918931 3.641588 5999
(More than 99 unique values)
Chó ý: cã thÓ xem thªm lÖnh codebook
3.9. T¹o b¶ng tÇn suÊt
T¹o b¶ng tÇn suÊt 1 chiÒu
Có ph¸p:
tabulate <tªn biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, missing nolabel]
tab1 <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, missing nolabel]
LÖnh n y t¹o b¶ng tÇn suÊt 1 chiÒu cña biÕn ®−îc chØ ra. LÖnh tabulate chØ cho phÐp cã 1 biÕn ®−îc chØ
ra, nÕu cã h¬n 1 biÕn ®−îc chØ ra th× Stata sÏ hiÓu l t¹o b¶ng tÇn suÊt 2 chiÒu.
C¸c tuú chän:
missing Cho phÐp c¸c quan s¸t kh«ng cã gi¸ trÞ (missing) ®−îc xÕp v o 1 lo¹i.
nolabel Cho phÐp hiÓn thÞ gi¸ trÞ sè cña biÕn, chø kh«ng ph¶i nh n biÕn
VÝ dô:
. tab sex
Gender of |
HH.head |
(1:M;2:F) | Freq. Percent Cum.](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-16-320.jpg)
![18
T¹o b¶ng tÇn suÊt 2 chiÒu
Có ph¸p:
tabulate <tªn biÕn 1> <tªn biÕn 2> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, chi2 missing nofreq cell
column row]
tab2 <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, chi2 missing nofreq cell column row]
LÖnh tablulate n y tÝnh v hiÓn thÞ b¶ng tÇn suÊt 2 chiÒu cña 2 biÕn ®−îc chØ ra. LÖnh tab2 t¹o b¶ng
tÇn suÊt 2 chiÒu cña tõng cÆp biÕn ®−îc chØ ra trong danh s¸ch biÕn.
VÝ dô:
. tab urban98 farm
1:urban | Type of HH (1:farm;
98; | 0:nonfarm)
0:rural 98 | non farm farm | Total
-----------+----------------------+----------
Rural | 1021 3248 | 4269
Urban | 1540 190 | 1730
-----------+----------------------+----------
Total | 2561 3438 | 5999
C¸c tuú chän:
chi2 Thùc hiÖn kiÓm ®Þnh gi¶ thiÕt l hai biÕn ®éc lËp](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-18-320.jpg)
![19
missing Cho phÐp c¸c quan s¸t kh«ng cã gi¸ trÞ ®−îc xÕp v o 1 lo¹i
nofreq Kh«ng hiÓn thÞ tÇn suÊt
cell HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c «
column HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c « theo cét
row HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c « theo h ng
VÝ dô:
. tab reg7 urban98, cell nof
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban | Total
-----------+----------------------+----------
region1 | 11.20 3.12 | 14.32
region2 | 13.05 6.53 | 19.59
region3 | 10.00 1.80 | 11.80
region4 | 8.37 4.20 | 12.57
region5 | 6.13 0.00 | 6.13
region6 | 8.57 8.48 | 17.05
region7 | 13.84 4.70 | 18.54
-----------+----------------------+----------
Total | 71.16 28.84 | 100.00
. tab farm urban98, column row
Type of HH | 1:urban 98; 0:rural
(1:farm; | 98
0:nonfarm) | Rural Urban | Total
-----------+----------------------+----------
non farm | 1021 1540 | 2561
| 39.87 60.13 | 100.00
| 23.92 89.02 | 42.69
-----------+----------------------+----------
farm | 3248 190 | 3438
| 94.47 5.53 | 100.00
| 76.08 10.98 | 57.31
-----------+----------------------+----------
Total | 4269 1730 | 5999
| 71.16 28.84 | 100.00
| 100.00 100.00 | 100.00
3.10. T¹o b¶ng thèng kª tæng hîp b»ng lÖnh tabulate…summarize
Có ph¸p:
tabulate <tªn biÕn 1> <tªn biÕn 2> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] , summarize(tªn biÕn 3)
[means standard freq missing ]
LÖnh n y t¹o b¶ng mét hoÆc hai chiÒu ®Þnh nghÜa bëi biÕn 1 hoÆc biÕn 2 v mçi « cho gi¸ trÞ thèng kª
trung b×nh, ®é lÖch chuÈn v tÇn suÊt cña biÕn 3.
VÝ dô:](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-19-320.jpg)
![21
tabstat <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, statistics(có ph¸p tkª [...]) by(tªn
biÕn) missing format[(%fmt)]]
LÖnh n y tÝnh to¸n c¸c thèng kª cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn cho tõng gi¸ trÞ cña biÕn
ph©n lo¹i (categorical) ®−îc chØ ra bëi by(tªn biÕn).
Chóng ta còng cã thÓ dïng cöa sæ lÖnh b»ng menu bar
VÝ dô:
. tabstat rlfood rlhhex1, stats(mean median) by(reg7)
Summary statistics: mean, p50
by categories of: reg7 (Code by 7 regions)
reg7 | rlfood rlhhex1
--------+--------------------
region1 | 5595.556 9560.349
| 5350.916 8536.373
-----------------------------
region2 | 6419.427 12951.14
| 5664.145 9997.146
-----------------------------
region3 | 5692.201 10885.38
| 5369.411 9022.334
-----------------------------
region4 | 6512.576 13525.41](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-21-320.jpg)
![22
| 5790.046 11077.51
-----------------------------
region5 | 5894.983 11217.05
| 5380.505 9421.447
-----------------------------
region6 | 9746.158 23515.01
| 8428.743 18514.39
-----------------------------
region7 | 6556.616 13068.11
| 6066.128 11043.99
-----------------------------
Total | 6787.898 14010.74
| 5951.567 10733.19
-----------------------------
C¸c tuú chän:
statistics(statname [...]) ChØ ra thèng kª cÇn tÝnh cho danh s¸ch biÕn
by(tªn biÕn) ChØ ra biÕn ph©n lo¹i (categorical)
Missing Gi¸ trÞ thiÕu (mising) cña biÕn lo¹i ®−îc xem nh− 1 lo¹i
format[(%fmt)] ChØ ra ®Þnh d¹ng cña sè liÖu hiÓn thÞ
Stata cho phÐp c¸c lo¹i thèng kª ®−îc chØ ra bëi statistics(có ph¸p thèng kª [...]) nh− sau:
Có ph¸p thèng kª ý nghÜa
mean Trung b×nh mean
count §Õm sè quan s¸t
n Gièng nh− lÖnh count (§Õm sè quan s¸t)
sum Tæng céng
max Gi¸ trÞ lín nhÊt
min Gi¸ trÞ nhá nhÊt
range Biªn ®é = Gi¸ trÞ lín nhÊt - Gi¸ trÞ nhá nhÊt
sd §é lÖch chuÈn
sdmean §é lÖch chuÈn cña trung b×nh = §é lÖch chuÈn / {(Sè quan s¸t)^0.5}
skewness §é lÖch cña ph©n phèi
kurtosis §é nhän
median Trung vÞ (Gièng nh− p50)
p1 1% ph©n vÞ
p5 5% ph©n vÞ
p10 10% ph©n vÞ
p25 25% ph©n vÞ
p50 50% ph©n vÞ (trung vÞ)](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-22-320.jpg)
![23
p75 75% ph©n vÞ
p90 90% ph©n vÞ
p95 95% ph©n vÞ
p99 99% ph©n vÞ
iqr p75 - p25
q t−¬ng ®−¬ng víi "p25 p50 p75"
VÝ dô:
. tabstat rlpcex1, stats(mean sd q) by(reg7) format(%5.1f)
Summary for variables: rlpcex1
by categories of: reg7 (Code by 7 regions)
reg7 | mean sd p25 p50 p75
--------+--------------------------------------------------
region1 | 2174.8 1265.1 1328.0 1792.1 2710.8
region2 | 3294.0 2511.9 1816.7 2532.5 3822.0
region3 | 2503.3 1918.0 1489.7 2001.2 2808.1
region4 | 2933.7 2260.5 1697.9 2362.2 3471.4
region5 | 2087.3 1285.4 1217.3 1850.8 2700.5
region6 | 5257.5 4005.7 2676.7 4154.1 6431.8
region7 | 2931.1 2137.2 1680.1 2321.9 3414.7
-----------------------------------------------------------
Total | 3188.7 2692.6 1671.1 2397.0 3711.9
-----------------------------------------------------------
3.12. T¹o b¶ng thèng kª tæng hîp b»ng lÖnh table
Có ph¸p:
table <biÕn dßng> [biÕn cét [biÕn cét trªn cïng]] [®iÒu kiÖn] [ph¹m vi] [quyÒn sè] [, contents(néi
dung) row col format(%fmt) missing]
LÖnh n y cho phÐp tÝnh c¸c thèng kª cña c¸c biÕn ®−îc chØ ra trong contents theo d¹ng b¶ng, trong ®ã
c¸c h ng ®−îc ®Þnh nghÜa bëi biÕn dßng, cßn c¸c cét ®−îc ®Þnh nghÜa bëi biÕn cét (v biÕn cét trªn
cïng). C¸c biÕn h ng v cét n y l c¸c biÕn ph©n lo¹i (categorical).
VÝ dô:
. table reg7 urban98 farm, contents(mean poor)
----------------------------------------------------
| Type of HH (1:farm; 0:nonfarm) and
| 1:urban 98; 0:rural 98
Code by 7 | ---- non farm ---- ------ farm ------
regions | Rural Urban Rural Urban
----------+-----------------------------------------
region1 | 19.35484 6.015038 65.7377 12.96296
region2 | 26.66667 4.624278 33.96524 15.21739](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-23-320.jpg)
![25
----------------------------------------
. table urban98 farm, contents(mean rlpcex1 mean rlhhex1) row col
format(%4.2f)
----------------------------------------
1:urban |
98; | Type of HH (1:farm;
0:rural | 0:nonfarm)
98 | non farm farm Total
----------+-----------------------------
Rural | 2835.83 2212.12 2361.29
| 13242.03 10120.89 10867.36
|
Urban | 5476.86 3232.17 5230.33
| 22984.44 11903.19 21767.43
|
Total | 4423.95 2268.49 3188.67
| 19100.41 10219.39 14010.74
----------------------------------------
4. Biªn tËp v söa ch÷a d÷ liÖu (Data manipulation)
4.1.T¹o biÕn míi
T¹o biÕn b»ng lÖnh generate
Có ph¸p:
generate <biÕn míi> = biÓu thøc [®iÒu kiÖn] [ph¹m vi]
LÖnh n y cho phÐp t¹o biÕn míi cã gi¸ trÞ b»ng gi¸ trÞ cña biÓu thøc ®−îc chØ ra.
VÝ dô:
. gen poor = 1 if rlpcex1 < 1790
(4222 missing values generated)
. gen nonpoor=1 if rlpcex1 >= 1790
(1777 missing values generated)
LÖnh t¹o biÕn gi¶ tabulate…generate
Có ph¸p:
tabulate <biÕn ph©n lo¹i>, generate(biÕn míi)
LÖnh generate cã thÓ kÕt hîp víi tab ®Ó t¹o c¸c biÕn gi¶ . BiÕn míi t¹o ra sÏ cã d¹ng l “biÕn míi 1”,
“biÕn míi 2”, “biÕn míi 3”, v..v. BiÕn n y chÝnh l c¸c biÕn gi¶ ®−îc t¹o ra trªn c¬ së cña biÕn ph©n
lo¹i.
VÝ dô:
. tab reg7, gen(region)
Code by 7 |](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-25-320.jpg)
![26
regions | Freq. Percent Cum.
------------+-----------------------------------
region1 | 859 14.32 14.32
region2 | 1175 19.59 33.91
region3 | 708 11.80 45.71
region4 | 754 12.57 58.28
region5 | 368 6.13 64.41
region6 | 1023 17.05 81.46
region7 | 1112 18.54 100.00
------------+-----------------------------------
Total | 5999 100.00
. tab1 region1 region2
-> tabulation of region1
reg7==regio |
n1 | Freq. Percent Cum.
------------+-----------------------------------
0 | 5140 85.68 85.68
1 | 859 14.32 100.00
------------+-----------------------------------
Total | 5999 100.00
-> tabulation of region2
reg7==regio |
n2 | Freq. Percent Cum.
------------+-----------------------------------
0 | 4824 80.41 80.41
1 | 1175 19.59 100.00
------------+-----------------------------------
Total | 5999 100.00
ë ®©y biÕn reg7 cã 7 gi¸ trÞ tõ 1 ®Õn 7 t−¬ng øng víi 7 biÕn gi¶ tõ region1 ®Õn region7 sÏ ®−îc t¹o ra.
BiÕn region1 nhËn gi¸ trÞ b»ng 1 nÕu nh− biÕn reg7 nhËn gi¸ trÞ 1, nÕu kh«ng th× b»ng 0. T−¬ng tù biÕn
region7 nhËn gi¸ trÞ 1 nÕu nh− biÕn reg7 b»ng 7.
ë vÝ dô trªn lÖnh tabulate…generate t−¬ng ®−¬ng víi 7 lÖnh sau:
gen region1=(reg7==1)
gen region2=(reg7==2)
…
gen region7=(reg7==7)
T¹o biÕn b»ng lÖnh egen
Có ph¸p:
egen <biÕn míi> = fcn(tham sè) [®iÒu kiÖn] [ph¹m vi] [, by(biÕn)]
LÖnh n y cho phÐp t¹o biÕn míi theo gi¸ trÞ cña h m sè ®−îc chØ ra bëi fcn. BiÕn míi n y sÏ nhËn gi¸
trÞ cè ®Þnh cho mäi quan s¸t. H m sè ë ®©y cã thÓ l :
count(exp) §Õm sè quan s¸t cña biÓu thøc](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-26-320.jpg)
![27
mean(exp) Cho gi¸ trÞ trung b×nh cña biÓu thøc
median(exp) Cho gi¸ trÞ trung vÞ cña biÓu thøc
sd(exp) Cho gi¸ trÞ ®é lÖch chuÈn cña biÓu thøc
C¸c h m sè kh¸c cã thÓ xem ë phÇn help egen.
VÝ dô:
. egen sumexp=sum(rlpcex1)
. sum sumexp
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
sumexp | 5999 1.91e+07 0 1.91e+07 1.91e+07
. egen g=median( food+ nonfood1)
. sum g
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
g | 5999 11063.6 0 11063.6 11063.6
Thay thÕ gi¸ trÞ cña biÕn
Có ph¸p:
replace <biÕn> = biÓu thøc [®iÒu kiÖn] [ph¹m vi]
LÖnh n y thay thÕ gi¸ trÞ cña biÕn hiÖn cã b»ng gi¸ trÞ míi x¸c ®Þnh bëi biÓu thøc exp.
VÝ dô:
replace poor=poor*100
replace pcexp = hhexp/hhsize
T¹o biÕn ph©n lo¹i b»ng lÖnh encode
Có ph¸p:
encode <biÕn> [®iÒu kiÖn] [ph¹m vi], generate(biÕn míi)
LÖnh n y cho phÐp t¹o biÕn ph©n lo¹i míi (categorical) kiÓu sè t−¬ng øng víi c¸c gi¸ trÞ cña biÕn kiÓu
ch÷ chØ ra bëi tªn biÕn (®−îc xÕp theo vÇn ch÷ c¸i).
VÝ dô:
. gen str15(mucsong) = "Kha"
. drop mucsong
. gen mucsong="Rat ngheo"
type mismatch
r(109);](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-27-320.jpg)
![28
. gen str15(mucsong)="Rat ngheo"
. replace mucsong="Ngheo" if rlpcex1<1790 & rlpcex1>1290
(1087 real changes made)
. replace mucsong="Khong ngheo" if rlpcex1>=1790
(4222 real changes made)
. tab mucsong
mucsong | Freq. Percent Cum.
----------------+-----------------------------------
Khong ngheo | 4222 70.38 70.38
Ngheo | 1087 18.12 88.50
Rat ngheo | 690 11.50 100.00
----------------+-----------------------------------
Total | 5999 100.00
. sum mucsong
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
mucsong | 0
. encode mucsong, gen(ma_ms)
. tab ma_ms
ma_ms | Freq. Percent Cum.
------------+-----------------------------------
Khong ngheo | 4222 70.38 70.38
Ngheo | 1087 18.12 88.50
Rat ngheo | 690 11.50 100.00
------------+-----------------------------------
Total | 5999 100.00
. sum ma_ms
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
ma_ms | 5999 1.411235 .6871957 1 3
T¹o biÕn b»ng lÖnh xtile
Có ph¸p:
xtile <biÕn míi> = biÓu thøc [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, nquantiles(#)]
LÖnh n y t¹o biÕn ph©n nhãm cho biÓu thøc theo ph©n vÞ. Trong ®ã nquantiles(#) chØ ra sè l−îng
ph©n vÞ.
VÝ dô: T¹o biÕn ngò vÞ ph©n theo chi tiªu
. xtile quinexp= rlpcex1, nq(5)
. tab quinexp](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-28-320.jpg)
![29
5 quantiles |
of rlpcex1 | Freq. Percent Cum.
------------+-----------------------------------
1 | 1200 20.00 20.00
2 | 1200 20.00 40.01
3 | 1200 20.00 60.01
4 | 1200 20.00 80.01
5 | 1199 19.99 100.00
------------+-----------------------------------
Total | 5999 100.00
. tab quinexp, sum( rlpcex1)
| Summary of comp.M&Reg price adj.pc
5 quantiles | tot exp
of rlpcex1 | Mean Std. Dev. Freq.
------------+------------------------------------
1 | 1184.3975 261.20537 1200
2 | 1803.6331 151.66604 1200
3 | 2408.4867 211.5407 1200
4 | 3390.1065 403.08913 1200
5 | 7160.021 3690.3672 1199
------------+------------------------------------
Total | 3188.6671 2692.5673 5999
4.2.§æi tªn biÕn
Có ph¸p:
rename <tªn biÕn có> <tªn biÕn míi>
LÖnh n y thùc hiÖn viÖc ®æi tªn cò cña mét biÕn sang tªn míi.
VÝ dô:
rename poor nguoingheo
rename rpcexp1 chitieu
4.3. LÖnh xo¸ biÕn, xo¸ quan s¸t
Có ph¸p:
drop <danh s¸ch biÕn> LÖnh n y xo¸ biÕn ®−îc chØ ra bëi danh s¸ch biÕn
drop <®iÒu kiÖn> LÖnh n y xo¸ quan s¸t tho¶ m n ®iÒu kiÖn biÓu thøc
drop <ph¹m vi> [®iÒu kiÖn] LÖnh n y xo¸ quan s¸t ®−îc chØ ra bëi ph¹m vi (v cã thÓ ph¶i tho¶
m n ®iÒu kiÖn biÓu thøc)
keep <danh s¸ch biÕn> LÖnh n y gi÷ l¹i c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn, c¸c biÕn
kh«ng ®−îc chØ ra sÏ bÞ xo¸ ®i
keep <®iÒu kiÖn> LÖnh n y gi÷ l¹i c¸c quan s¸t tho¶ m n ®iÒu kiÖn biÓu thøc, c¸c quan
s¸t kh¸c sÏ bÞ xo¸ ®i
keep <ph¹m vi> [®iÒu kiÖn] LÖnh n y gi÷ l¹i c¸c quan s¸t ®−îc chØ ra bëi ph¹m vi (v cã thÓ tho¶
m n ®iÒu kiÖn biÓu thøc), c¸c quan s¸t kh¸c sÏ bÞ xo¸ ®i.](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-29-320.jpg)
![30
VÝ dô:
drop poor urban98 Xo¸ 2 biÕn poor v urban98
drop if sex==1 Xo¸ c¸c quan s¸t cã biÕn sex nhËn gi¸ trÞ b»ng 1
drop in 1/20 Xo¸ quan s¸t tõ 1 ®Õn 20
keep househol ChØ gi÷ l¹i biÕn househol, c¸c biÕn kh¸c bÞ xo¸ ®i
keep in f/50 Gi÷ l¹i quan s¸t tõ ®Çu tiªn ®Õn 50, c¸c quan s¸t kh¸c bÞ xo¸ ®i
4.4. LÖnh ®æi gi¸ trÞ cña biÕn ph©n lo¹i
Có ph¸p:
recode <tªn biÕn> gi¸ trÞ cò = gi¸ trÞ míi [®iÒu kiÖn] [ph¹m vi]
LÖnh n y ®æi gi¸ trÞ cña biÕn ph©n lo¹i theo c¸c quy t¾c ®−îc chØ ra ë sau ®ã.
VÝ dô:
. recode sex 0=1
(0 changes made)
. recode sex . = 0
(0 changes made)
. recode hhsize 1/5=1 6/10 = 2 * = 3
(5785 changes made)
. tab hhsize
Household |
size | Freq. Percent Cum.
------------+-----------------------------------
1 | 4164 69.41 69.41
2 | 1786 29.77 99.18
3 | 49 0.82 100.00
------------+-----------------------------------
Total | 5999 100.00
. tab urban98
1:urban 98; |
0:rural 98 | Freq. Percent Cum.
------------+-----------------------------------
Rural | 4269 71.16 71.16
Urban | 1730 28.84 100.00
------------+-----------------------------------
Total | 5999 100.00
. recode urban98 0=1 1=0
(5999 changes made)
. tab urban98
1:urban 98; |](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-30-320.jpg)
![31
0:rural 98 | Freq. Percent Cum.
------------+-----------------------------------
Rural | 1730 28.84 28.84
Urban | 4269 71.16 100.00
------------+-----------------------------------
Total | 5999 100.00
4.5. LÖnh g¸n nh·n cho biÕn
G¸n nh·n cho biÕn
Có ph¸p:
label variable <tªn biÕn> “Nh·n cña biÕn”
LÖnh n y g¸n nh n l mét dÉy ký tù cho biÕn.
VÝ dô:
. gen ngheo=poor
. des ngheo
storage display value
variable name type format label variable label
---------------------------------------------------------------------------
ngheo float %9.0g
. tab ngheo
ngheo | Freq. Percent Cum.
------------+-----------------------------------
0 | 4222 70.38 70.38
1 | 1777 29.62 100.00
------------+-----------------------------------
Total | 5999 100.00
. label var ngheo "Nguoi co thu nhap duoi chuan ngheo"
. tab ngheo
Nguoi co |
thu nhap |
duoi chuan |
ngheo | Freq. Percent Cum.
------------+-----------------------------------
0 | 4222 70.38 70.38
1 | 1777 29.62 100.00
------------+-----------------------------------
Total | 5999 100.00
. des ngheo
storage display value
variable name type format label variable label
----------------------------------------------------------------------------
ngheo float %9.0g Nguoi co thu nhap duoi chuan
ngheo
G¸n gi¸ trÞ cho biÕn ph©n lo¹i
label define <tªn bé nh·n> # "nh·n" [# "nh·n" ...] [, add modify]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-31-320.jpg)
![32
label dir
label list <tªn bé nh·n>
label drop {tªn bé nh·n [tªn bé nh·n ...] | _all}
label values <tªn biÕn> [tªn bé nh·n]
LÖnh label define g¸n nh n cho mét bé gi¸ trÞ sè. Tªn cña bé nh n ®−îc chØ ra sau tõ kho¸ define, # l
gi¸ trÞ sè, “nh·n” l chuçi ký tù t−¬ng øng víi gi¸ trÞ sè ®Êy. Cã hai tuú chän ë ®©y: tuú chän add
thªm gi¸ trÞ v nh n t−¬ng øng v o 1 bé nh n ® cã s½n. Tuú chän modify cho phÐp söa ch÷a gi¸ trÞ v
nh n cña 1 bé nh n ® cã s½n.
LÖnh label dir hiÓn thÞ nh÷ng bé nh n cã s½n, cßn lÖnh label list hiÓn thÞ gi¸ trÞ cña bé nh n ®−îc chØ
ra. LÖnh label drop xo¸ c¸c bé nh n cã s½n.
VÝ dô:
T¹o nh n cã tªn l nngheo víi gi¸ trÞ 1 cã nghÜa l ng−êi nghÌo, cßn 0 cã nghÜa l ng−êi kh«ng nghÌo.
. label define nngheo 0 "Ngheo" 1 "Khong ngheo"
. label dir
nngheo
region
loaiho
diploma
urban
agegroup
. label list nngheo
nngheo:
0 Khong ngheo
1 Ngheo
. label drop _all
. label dir
LÖnh label values sÏ g¸n c¸c nh n cña 1 bé nh n cho c¸c gi¸ trÞ sè cña 1 biÕn ph©n lo¹i.
VÝ dô:
. tab ngheo
ngheo | Freq. Percent Cum.
------------+-----------------------------------
0 | 4222 70.38 70.38
1 | 1777 29.62 100.00
------------+-----------------------------------
Total | 5999 100.00
. list ngheo in 1/5
ngheo
1. 1](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-32-320.jpg)
![33
2. 0
3. 1
4. 1
5. 0
. label values ngheo nngheo
. tab ngheo
ngheo | Freq. Percent Cum.
------------+-----------------------------------
Ngheo | 4222 70.38 70.38
Khong ngheo | 1777 29.62 100.00
------------+-----------------------------------
Total | 5999 100.00
. list ngheo in 1/5
ngheo
1. Khong ngheo
2. Ngheo
3. Khong ngheo
4. Khong ngheo
5. Ngheo
4.6. S¾p xÕp sè liÖu
Có ph¸p:
sort <danh s¸ch biÕn> [ph¹m vi]
gsort [+|-]tªn biÕn [[+|-]tªn biÕn [...]]
LÖnh sort s½p xÕp quan s¸t theo thø tù t¨ng dÇn cña gi¸ trÞ cña c¸c biÕn ®−îc chØ ra trong danh s¸ch
biÕn.
LÖnh gsort cho phÐp s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña cña c¸c biÕn (danh s¸ch biÕn), nÕu
dÊu + ®−îc chØ ra (®©y còng l gi¸ trÞ ngÇm ®Þnh), hoÆc theo thø tù gi¶m dÇn, nÕu dÊu - ®−îc chØ ra.
VÝ dô:
sort reg7 hhsize LÖnh n y s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña biÕn vïng reg7, trong
mçi vïng c¸c quan s¸t l¹i ®−îc s½p xÕp theo thø tù t¨ng dÇn cña biÕn quy m«
hé hhsize.
gsort reg7 –hhsize LÖnh n y s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña biÕn vïng reg7, nh−ng
trong mçi vïng c¸c quan s¸t l¹i ®−îc s½p xÕp theo thø tù gi¶m dÇn cña biÕn
quy m« hé hhsize.
4.7. Trén sè liÖu
LÖnh thu gän sè liÖu - collapse
Có ph¸p:
collapse <biÓu thøc thèng kª> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, by(danh s¸ch biÕn)]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-33-320.jpg)
![34
trong ®ã:
BiÓu thøc thèng kª l danh s¸ch c¸c thèng kª v c¸c biÕn t−¬ng øng. C¸c thèng kª ®−îc ký hiÖu nh−
môc 3.12 cña ch−¬ng n y.
LÖnh collapse sÏ t¹o ra mét tÖp sè liÖu míi bao gåm c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn, víi c¸c
gi¸ trÞ ®−îc tÝnh theo thèng kª t−¬ng øng. C¸c quan s¸t cña tÖp sè liÖu cò sÏ ®−îc nhãm l¹i theo c¸c gi¸
trÞ cïng lo¹i cña biÕn ®−îc chØ ra bëi by(danh s¸ch biÕn).
VÝ dô:
Chóng ta cã file sè liÖu vÒ thu nhËp v chi tiªu cña c¸c hé th nh viªn trong gia ®×nh:
ma_tv ma_ho thunhap Chitieu
1 101 200 500
2 101 1200 400
3 101 0 200
4 101 0 200
1 102 3200 500
2 102 1200 320
3 102 200 200
1 103 300 500
2 103 2100 250
3 103 0 300
4 103 0 300
1 104 4300 800
2 104 3500 500
3 104 300 500
4 104 0 300
5 104 0 200
6 104 0 200
Chóng ta sÏ dïng lÖnh collapse ®Ó t¹o file vÒ thu nhËp v chi tiªu b×nh qu©n cña c¸c hé, v t¹o thªm 1
biÕn vÒ qui m« hé.
. gen quimo=1
. collapse (mean) thunhap (mean) chitieu (sum) quimo, by(ma_ho)
TÖp sè liÖu míi cã d¹ng:
ma_ho thunhap chitieu quimo
101 350 325 4
102 1533.33 340 3
103 600 337.5 4
104 1350 416.667 6
KÕt hîp sè liÖu - lÖnh merge
Có ph¸p:
merge [danh s¸ch biÕn] using <tªn tÖp sö dông> [, update replace]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-34-320.jpg)
![37
Có ph¸p:
reshape wide <tªn biÕn>, i(danh s¸ch biÕn) [ j(tªn biÕn [values]) ... ]
reshape long <tªn biÕn>, i(danh s¸ch biÕn) [ j(tªn biÕn [values]) ... ]
reshape wide
reshape long
LÖnh n y cho phÐp chuyÓn sè liÖu tõ d¹ng ngang sang sè liÖu d¹ng däc (tuú chän long), v tõ d¹ng däc
sang d¹ng ngang (tuú chän wide). i(danh s¸ch biÕn) chØ ra biÕn x¸c ®Þnh (indentifying variables) dïng
®Ó ph©n biÖt c¸c quan s¸t víi nhau trong sè liÖu d¹ng ngang (gäi l quan s¸t cÊp 1). j(tªn biÕn) chØ ra
biÕn dïng ®Ó ph©n biÖt gi÷a c¸c quan s¸t cÊp 2 ë sè liÖu d¹ng däc.
VÝ dô 1:
Chóng ta cã thÓ sè liÖu d¹ng b¶ng ngang nh− mét ma trËn nh− sau:
- i - -------------------- xÞj -------------------
maho quimo thunhap95 thunhap96 thunhap97
101 5 4500 4400 5400
102 4 3400 3300 3700
103 6 5000 5400 5500
sè liÖu n y sÏ ®−îc chuyÓn sang d¹ng b¶ng däc nh− sau:
- i - - j - - xji -
maho quimo nam thunhap
101 5 95 4500
101 5 96 4400
101 5 97 5400
102 4 95 3400
102 4 96 3300
102 4 97 3700
103 6 95 5000
103 6 96 5400
103 6 97 5500
V lÖnh reshape sÏ ®−îc viÕt nh− sau:
. reshape long thunhap, i(maho) j(nam)
(note: j = 95 96 97)
Data wide -> long
---------------------------------------------------------------------
Number of obs. 3 -> 9
Number of variables 5 -> 4
j variable (3 values) -> nam
xij variables:
thunhap95 thunhap96 thunhap97 -> thunhap
---------------------------------------------------------------------
* Va chuyen nguoc lai tu dang doc sang dang ngang nhu sau
. reshape wide thunhap, i(maho) j(nam)
(note: j = 95 96 97)](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-37-320.jpg)
![40
region6 | 9447.7077 4535.0816 1023
region7 | 14653.702 6639.8297 1112
------------+------------------------------------
Total | 12636.546 6597.6574 5999
. di 2688.5003*5999
16128313
. di 12636.546*5999
75806639
5.2. C¸c lùa chän vÒ quyÒn sè
Stata cho phÐp sö dông 4 lo¹i lo¹i quyÒn sè sau ®©y:
fweights: quyÒn sè tÇn suÊt (frequency weights), Stata sÏ hiÓu quyÒn sè ë ®©y cã nghÜa l sè lÇn
m mçi quan s¸t mçi quan s¸t ®−îc lÆp l¹i trong tÝnh to¸n.
pweights: quyÒn sè chän mÉu (sampling weights), Stata sÏ hiÓu quyÒn sè l gi¸ trÞ nghÞch ®¶o
cña x¸c suÊt ®−îc chän v o mÉu, hay sè phÇn tö trong t«ng thÓ m mçi quan s¸t trong
mÉu ®¹i diÖn.
aweights quyÒn sè ph©n tÝch (analytical weights), Stata sÏ hiÓu quyÒn sè tû lÖ nghÞch víi ph−¬ng
sai cña quan s¸t.
iweights quyÒn sè quan träng (importance weights), ®©y l quyÒn sè chØ møc ®é quan träng cña
c¸c quan s¸t.
§èi víi §iÒu tra møc sèng c¸c lÖnh sö dông quyÒn sè pweights v fweights.
VÝ dô:
. sum poor
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
poor | 5999 29.6216 45.66255 0 100
. sum poor [fw=hhsize]
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
poor | 28509 34.17517 47.43051 0 100
.
.
. tab reg7 urban98
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban | Total
-----------+----------------------+----------
region1 | 672 187 | 859
region2 | 783 392 | 1175
region3 | 600 108 | 708
region4 | 502 252 | 754
region5 | 368 0 | 368](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-40-320.jpg)
![41
region6 | 514 509 | 1023
region7 | 830 282 | 1112
-----------+----------------------+----------
Total | 4269 1730 | 5999
.
. tab reg7 urban98 [fw= hhsizewt]
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban | Total
-----------+----------------------+----------
region1 | 11993763 1570583 | 13564346
region2 | 11057932 3812871 | 14870803
region3 | 9582621 906048 | 10488669
region4 | 5618709 2520372 | 8139081
region5 | 2783821 0 | 2783821
region6 | 4545303 5119702 | 9665005
region7 | 13220727 3074190 | 16294917
-----------+----------------------+----------
Total | 58802876 17003766 | 75806642
. tab reg7 urban98 , sum(hhsize) means
Means of Household size
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban | Total
-----------+----------------------+----------
region1 | 5.1205357 3.7326203 | 4.8183935
region2 | 4.045977 4.0459184 | 4.0459574
region3 | 4.6666667 4.6759259 | 4.6680791
region4 | 4.8027888 5.1190476 | 4.9084881
region5 | 5.7065217 . | 5.7065217
region6 | 5.0719844 4.7131631 | 4.8934506
region7 | 5.1373494 4.3971631 | 4.9496403
-----------+----------------------+----------
Total | 4.8702272 4.4612717 | 4.752292
. tab reg7 urban98 [fw=wt], sum(hhsize) means
Means and Number of Observations of Household size
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban | Total
-----------+----------------------+----------
region1 | 5.1328749 3.6698008 | 4.9063857
| 2336656 427975 | 2764631
-----------+----------------------+----------
region2 | 4.0564115 3.987975 | 4.0386415
| 2726038 956092 | 3682130
-----------+----------------------+----------](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-41-320.jpg)
![42
region3 | 4.6508908 4.6530097 | 4.6510738
| 2060384 194723 | 2255107
-----------+----------------------+----------
region4 | 4.8136253 5.132367 | 4.9080132
| 1167251 491074 | 1658325
-----------+----------------------+----------
region5 | 5.6609112 . | 5.6609112
| 491762 0 | 491762
-----------+----------------------+----------
region6 | 5.0486426 4.6174858 | 4.8106956
| 900302 1108764 | 2009066
-----------+----------------------+----------
region7 | 5.1494132 4.3925283 | 4.9872852
| 2567424 699868 | 3267292
-----------+----------------------+----------
Total | 4.8003065 4.3841133 | 4.7002214
| 12249817 3878496 | 16128313
.
. table reg7 urban98 , c(mean poor) col row format(%4.1f)
-------------------------------
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban Total
----------+--------------------
region1 | 61.5 8.0 49.8
region2 | 32.6 5.9 23.7
region3 | 44.8 10.2 39.5
region4 | 37.3 11.5 28.6
region5 | 47.3 47.3
region6 | 12.5 2.2 7.3
region7 | 35.8 10.3 29.3
|
Total | 38.9 6.8 29.6
-------------------------------
. table reg7 urban98 [pw=hhsizewt], c(mean poor) col row format(%4.1f)
-------------------------------
| 1:urban 98; 0:rural
Code by 7 | 98
regions | Rural Urban Total
----------+--------------------
region1 | 65.2 8.3 58.6
region2 | 36.1 7.0 28.7
region3 | 51.3 14.3 48.1
region4 | 43.6 16.6 35.2
region5 | 52.4 52.4
region6 | 13.0 2.9 7.6
region7 | 42.0 15.3 36.9
|
Total | 45.5 9.2 37.4
-------------------------------](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-42-320.jpg)
![43
Ch−¬ng III: KiÓm ®Þnh gi¶ thiÕt vµ ph©n tÝch håi quy
1. ¦íc l−îng v kiÓm ®Þnh gi¶ thiÕt (Estimation and hypothesis testing)
1.1. ¦íc l−îng gi¸ trÞ trung b×nh b»ng kho¶ng tin cËy
Có ph¸p:
ci [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, level(#) binomial poisson exposure(tªn
biÕn) total]
LÖnh n y tÝnh sai sè chuÈn v kho¶ng tin cËy cho gi¸ trÞ trung b×nh cña mÉu theo quy luËt chuÈn, nhÞ
thøc v Poatx«ng.
C¸c tuú chän:
level(#) chØ ®Þnh møc ®é tin cËy cho −íc l−îng kho¶ng tin cËy. # nhËn
gi¸ trÞ tõ 10 ®ªn 99, gi¸ trÞ ngÇm ®Þnh l 95.
binomial ¸p dông cho quy luËt nhÞ thøc
poisson ¸p dông cho quy luËt Poatx«ng
exposure(tªn biÕn) ¸p dông cho quy luËt Poatx«ng, tªn biÕn chØ ra biÕn “thêi
l−îng” (th«ng th−êng l thêi gian hoÆc diÖn tÝch) m trong ®ã
x¶y ra c¸c “sù kiÖn” ®−îc chØ ra bëi danh s¸ch biÕn
total dïng khi ma “by prefix” ®−îc sö dung, yªu cÇu −íc l−îng
kho¶ng tin cËy cho to n bé nhãm.
VÝ dô:
. ci poor
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 5999 29.6216 .5895501 28.46587 30.77733
.
.
. sort reg7
. by reg7: ci poor, total
_______________________________________________________________________________
-> reg7 = region1
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 859 49.82538 1.706961 46.47507 53.17569
_______________________________________________________________________________
-> reg7 = region2
Variable | Obs Mean Std. Err. [95% Conf. Interval]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-43-320.jpg)
![44
-------------+-------------------------------------------------------------
poor | 1175 23.65957 1.240357 21.22601 26.09314
_______________________________________________________________________________
-> reg7 = region3
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 708 39.54802 1.838899 35.93767 43.15838
_______________________________________________________________________________
-> reg7 = region4
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 754 28.64721 1.64759 25.4128 31.88163
_______________________________________________________________________________
-> reg7 = region5
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 368 47.28261 2.606121 42.1578 52.40741
_______________________________________________________________________________
-> reg7 = region6
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 1023 7.331378 .8153306 5.731465 8.931292
_______________________________________________________________________________
-> reg7 = region7
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 1112 29.31655 1.365709 26.63689 31.99621
_______________________________________________________________________________
-> Total
Variable | Obs Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
poor | 5999 29.6216 .5895501 28.46587 30.77733
Chó ý:
C¸c lÖnh −íc l−îng cã thÓ ®−îc sö dông khi biÕt c¸c tham sè vÒ mÉu. §©y cã thÓ ®−îc gäi l “c¸c lÖnh
sö dông tham sè trùc tiÕp” (Commands using immediate arguments). C¸c lÖnh n y rÊt h÷u dông khi
chóng ta kh«ng cã sè liÖu gèc vÒ biÕn.
cii <sè quan s¸t> <gi¸ trÞ trungb×nh> <®é lÖch chuÈn> [, level(#) ] (ph©n phèi chuÈn)
cii <sè quan s¸t> <sè lÇn th nh c«ng cña quan s¸t> [, level(#) ] (ph©n phèi nhÞ thøc)](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-44-320.jpg)
![45
#obs chØ ra sè quan s¸t, #succ chØ ra sè lÇn gi¸ trÞ biÕn nhËn gi¸ trÞ t−¬ng øng víi phÐp thö th nh c«ng
(th«ng th−êng nhËn gi¸ trÞ b»ng 1)
cii <gi¸ trÞ thêi l−îng> <sè lÇn sù kiÖn x¶y ra> poisson [ level(#) ] (ph©n phèi Poatx«ng)
VÝ dô:
. cii 5999 1777, level (90)
-- Binomial Exact --
Variable | Obs Mean Std. Err. [90% Conf. Interval]
-------------+-------------------------------------------------------------
| 5999 .296216 .005895 .2865107 .3060676
. cii 12 27, poisson
-- Poisson Exact --
Variable | Exposure Mean Std. Err. [95% Conf. Interval]
-------------+-------------------------------------------------------------
| 12 2.25 .4330127 1.483144 3.273587
1.2. KiÓm ®Þnh gi¶ thuyÕt thèng kª
1.2.1. KiÓm ®Þnh gi¸ trÞ trung b×nh cña mÉu
Ph©n phèi kh«ng mét
Có ph¸p:
prtest <biÕn>= # [®iÒu kiÖn] [ph¹m vi] [, level(#)]
LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ tû lÖ gi¸ trÞ cña biÕn ph©n phèi theo quy luËt kh«ng mét
(Ho: p = p0).
VÝ dô:
. prtest poor=0.44 if reg7==1
One-sample test of proportion poor: Number of obs = 859
----------------------------------------------------------------------------
Variable | Mean Std. Err. z P>|z| [95% Conf. Interval]
---------+------------------------------------------------------------------
poor | .4982538 .0170597 29.2065 0.0000 .4648174 .5316901
----------------------------------------------------------------------------
Ho: proportion(poor) = .44
Ha: poor < .44 Ha: poor ~= .44 Ha: poor > .44
z = 3.440 z = 3.440 z = 3.440
P < z = 0.9997 P > |z| = 0.0006 P > z = 0.0003
prtest <biÕn 1> = <tªn biÕn2> [®iÒu kiÖn] [ph¹m vi] [, level(#)]
LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña tû lÖ cña hai gi¸ trÞ biÕn ®−îc chØ ra bëi
tªn biÕn (Ho: pX = pY).](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-45-320.jpg)
![46
VÝ dô: KiÓm ®Þnh xem tû lÖ nghÌo ®ãi gi÷a vïng 2 v vïng 4 cã khac nhau kh«ng:
. gen poor2=poor if reg7==2
(4824 missing values generated)
. gen poor4=poor if reg7==4
(5245 missing values generated)
. prtest poor2 = poor4
Two-sample test of proportion poor2: Number of obs = 1175
poor4: Number of obs = 754
------------------------------------------------------------------------------
Variable | Mean Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
poor2 | .2365957 .0123983 19.0829 0.0000 .2122955 .2608959
poor4 | .2864721 .016465 17.3989 0.0000 .2542014 .3187429
---------+--------------------------------------------------------------------
diff | -.0498764 .020611 -.0902732 -.0094796
| under Ho: .0203666 -2.44893 0.0143
------------------------------------------------------------------------------
Ho: proportion(poor2) - proportion(poor4) = diff = 0
Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0
z = -2.449 z = -2.449 z = -2.449
P < z = 0.0072 P > |z| = 0.0143 P > z = 0.9928
prtest <biÕn> [®iÒu kiÖn] [ph¹m vi], by(biÕn ph©n nhãm) [level(#)]
LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña tû lÖ cña hai nhãm ®−îc chØ ra bëi biÕn
ph©n nhãm (Ho: pX1 = pX2).
VÝ dô:
. prtest poor, by(sex)
Two-sample test of proportion 1: Number of obs = 4375
2: Number of obs = 1624
------------------------------------------------------------------------------
Variable | Mean Std. Err. z P>|z| [95% Conf. Interval]
---------+--------------------------------------------------------------------
1 | .3248 .00708 45.8755 0.0000 .3109234 .3386766
2 | .2192118 .0102661 21.353 0.0000 .1990906 .239333
---------+--------------------------------------------------------------------
diff | .1055882 .0124708 .0811459 .1300304
| under Ho: .0132673 7.95855 0.0000
------------------------------------------------------------------------------
Ho: proportion(1) - proportion(2) = diff = 0
Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0
z = 7.959 z = 7.959 z = 7.959
P < z = 1.0000 P > |z| = 0.0000 P > z = 0.0000](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-46-320.jpg)
![47
Ph©n phèi nhÞ thøc
Có ph¸p:
bitest <biÕn> = #p [quyÒn sè] [®iÒu kiÖn] [ph¹m vi]
LÖnh n y kiÓm ®Þnh gi¶ thuyÕt vÒ tham sè p trong quy luËt nhÞ thøc (x¸c suÊt th nh c«ng cña phÐp thö)
cña biÕn ®−îc chØ ra bëi tªn biÕn. (Ho: p = p0)
VÝ dô:
. bitest poor=0.44 if reg7==1
Variable | N Observed k Expected k Assumed p Observed p
-------------+------------------------------------------------------------
poor | 859 428 377.96 0.44000 0.49825
Pr(k >= 428) = 0.000344 (one-sided test)
Pr(k <= 428) = 0.999732 (one-sided test)
Pr(k <= 328 or k >= 428) = 0.000660 (two-sided test)
. bitesti 859 428 0.44
N Observed k Expected k Assumed p Observed p
------------------------------------------------------------
859 428 377.96 0.44000 0.49825
Pr(k >= 428) = 0.000344 (one-sided test)
Pr(k <= 428) = 0.999732 (one-sided test)
Pr(k <= 328 or k >= 428) = 0.000660 (two-sided test)
Quy luËt ph©n phèi chuÈn
Có ph¸p:
ttest <biÕn> = # [®iÒu kiÖn] [ph¹m vi] [, level(#) ]
LÖnh n y kiÓm ®Þnh gi¶ thuyÕt vÒ gi¸ trÞ cña tham sè trung b×nh cña biÕn ngÉu nhiªn tu©n theo quy luËt
chuÈn ®−îc chØ ra bëi tªn biÕn (Ho: µ = µ0)
VÝ dô:
. ttest rlpcex1=3200
One-sample t test
------------------------------------------------------------------------------
Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
rlpcex1 | 5999 3188.667 34.76379 2692.567 3120.518 3256.817
------------------------------------------------------------------------------
Degrees of freedom: 5998
Ho: mean(rlpcex1) = 3200
Ha: mean < 3200 Ha: mean ~= 3200 Ha: mean > 3200
t = -0.3260 t = -0.3260 t = -0.3260
P < t = 0.3722 P > |t| = 0.7444 P > t = 0.6278](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-47-320.jpg)
![48
ttest <biÕn 1> = <biÕn 2> [®iÒu kiÖn] [ph¹m vi] [, unpaired unequal level(#) ]
LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt r»ng hai biÕn cã gi¸ trÞ trung b×nh b»ng nhau. (Ho: µX = µY).
C¸c tuú chän:
unpaired Sè liÖu cña hai biÕn kh«ng cïng cÆp
unequal Phu¬ng sai cña hai biÕn kh«ng b»ng nhau
VÝ dô:
. ttest poor2=poor4, unpaired unequal
Two-sample t test with unequal variances
------------------------------------------------------------------------------
Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
poor2 | 1175 .2365957 .0124036 .425173 .2122601 .2609314
poor4 | 754 .2864721 .0164759 .4524128 .254128 .3188163
---------+--------------------------------------------------------------------
combined | 1929 .2560912 .0099404 .436586 .2365962 .2755863
---------+--------------------------------------------------------------------
diff | -.0498764 .0206229 -.0903285 -.0094243
------------------------------------------------------------------------------
Satterthwaite's degrees of freedom: 1532.64
Ho: mean(poor2) - mean(poor4) = diff = 0
Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0
t = -2.4185 t = -2.4185 t = -2.4185
P < t = 0.0079 P > |t| = 0.0157 P > t = 0.9921
ttest <biÕn> [®iÒu kiÖn] [ph¹m vi], by(biÕn ph©n nhãm) [ unequal level(#) ]
LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña gi¸ trÞ trung b×nh cña hai nhãm ®−îc chØ
ra bëi biÕn ph©n nhãm (Ho: µX1 = µX2).
VÝ dô:
. ttest rlpcex1, by(sex)
Two-sample t test with equal variances
------------------------------------------------------------------------------
Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
1 | 4375 2980.906 36.74795 2430.648 2908.862 3052.951
2 | 1624 3748.368 80.18189 3231.241 3591.097 3905.638
---------+--------------------------------------------------------------------
combined | 5999 3188.667 34.76379 2692.567 3120.518 3256.817
---------+--------------------------------------------------------------------
diff | -767.4613 77.6155 -919.6156 -615.3071
------------------------------------------------------------------------------
Degrees of freedom: 5997](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-48-320.jpg)
![49
Ho: mean(1) - mean(2) = diff = 0
Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0
t = -9.8880 t = -9.8880 t = -9.8880
P < t = 0.0000 P > |t| = 0.0000 P > t = 1.0000
1.2.2. KiÓm ®Þnh gi¸ trÞ ®é lÖch chuÈn
Có ph¸p:
sdtest <biÕn> = # [®iÒu kiÖn] [ph¹m vi] [, level(#) ]
sdtest <biÕn 1> = <biÕn 2> [®iÒu kiÖn] [ph¹m vi] [, level(#) ]
sdtest <biÕn> [®iÒu kiÖn] [ph¹m vi] , by(biÕn ph©n nhãm) [ level(#) ]
LÖnh n y kiÓm dÞnh tham sè ®é lÖch chuÈn cña biÕn ngÉu nhiªn tu©n theo quy luËt chuÈn ®−îc chØ ra
bëi tªn biÕn. Có ph¸p cña lÖn n y t−¬ng tù víi có ph¸p cña lÖnh ttest
VÝ dô:
. sum rlpcex1
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
rlpcex1 | 5999 3188.667 2692.567 357.318 45801.71
. sdtest rlpcex1=2700
One-sample test of variance
------------------------------------------------------------------------------
Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval]
---------+--------------------------------------------------------------------
rlpcex1 | 5999 3188.667 34.76379 2692.567 3120.518 3256.817
------------------------------------------------------------------------------
Ho: sd(rlpcex1) = 2700
chi2(5998) = 5965.022
Ha: sd(rlpcex1) < 2700 Ha: sd(rlpcex1) ~= 2700 Ha: sd(rlpcex1) > 2700
P < chi2 = 0.3838 2*(P < chi2) = 0.7676 P > chi2 = 0.6162
2. Ph©n tÝch t−¬ng quan v håi quy (Correlation and regression)
2.1. Ph©n tÝch t−¬ng quan
Có ph¸p:
correlate [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, means covariance _coef wrap]
LÖnh n y tÝnh ma trËn hÖ sè t−ong quan (correlation coefficient), hoÆc hiÖp ph−¬ng sai (covariance)
cho c¸c biÕn ®−îc liÖt kª trong danh s¸ch biÕn. Sè quan s¸t ®−îc dïng l sè quan s¸t cña biÕn cã Ýt
quan s¸t nhÊt.
C¸c tuú chän:](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-49-320.jpg)
![50
means HiÓn thÞ c¸c thèng kª kh¸c nh− gi¸ trÞ trung b×nh, ®é lÖch chuÈn, gi¸
trÞ lín nhÊt, nhá nhÊt
covariance §−a ra ma trËn hiÖp ph−¬ng sai thay v× hÖ sè t−¬ng quan
_coef TÝnh ma trËn tu¬ng quan cña c¸c hÖ sè cña −íc l−îng gÇn nhÊt
wrap HiÓn thÞ c¸c dßng cña ma trËn liÒn nhau nÕu cã qua nhiÒu c¸c biÕn
®−îc liÖt kª
VÝ dô:
. corr hhsize poor rlpcex1 sex
(obs=5999)
| hhsize poor rlpcex1 sex
-------------+------------------------------------
hhsize | 1.0000
poor | 0.2425 1.0000
rlpcex1 | -0.2172 -0.4452 1.0000
sex | -0.2570 -0.1028 0.1267 1.0000
. corr hhsize poor rlpcex1 sex, means cov
(obs=5999)
Variable | Mean Std. Dev. Min Max
-------------+----------------------------------------------------
hhsize | 4.752292 1.954292 1 19
poor | .296216 .4566255 0 1
rlpcex1 | 3188.667 2692.567 357.318 45801.71
sex | 1.270712 .4443645 1 2
| hhsize poor rlpcex1 sex
-------------+------------------------------------
hhsize | 3.81926
poor | .216435 .208507
rlpcex1 | -1142.93 -547.335 7.2e+06
sex | -.223195 -.020849 151.543 .19746
pwcorr [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, obs sig print(#) star(#)]
LÖnh n y tÝnh hÖ sè t−¬ng quan cho tõng cÆp biÕn ®−îc chØ ra bëi danh s¸ch biÕn.
C¸c tuú chän:
obs HiÓn thÞ sè quan s¸t dïng ®Ó tÝnh hÖ sè t−¬ng quan
sig HiÓn thÞ møc ý nghÜa cña c¸c hÖ sè t−¬ng quan
print(#) ChØ ra møc ý nghÜa theo ®ã chØ c¸c hÖ sè t−¬ng quan cã møc ý
nghÜa nhá h¬n møc n y míi ®−îc hiÓn thÞ
star(#) §¸nh dÊu sao ®èi víi c¸c hÖ sè t−¬ng quan cã møc ý nghÜ nhá h¬n](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-50-320.jpg)
![51
møc ®−îc chØ ra bëi star
VÝ dô:
. pwcorr hhsize poor rlpcex1 sex, obs sig star(5)
| hhsize poor rlpcex1 sex
-------------+------------------------------------
hhsize | 1.0000
|
| 5999
|
poor | 0.2425* 1.0000
| 0.0000
| 5999 5999
|
rlpcex1 | -0.2172* -0.4452* 1.0000
| 0.0000 0.0000
| 5999 5999 5999
|
sex | -0.2570* -0.1028* 0.1267* 1.0000
| 0.0000 0.0000 0.0000
| 5999 5999 5999 5999
|
pcorr <biÕn> <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi]
LÖnh n y tÝnh hÖ sè t−¬ng quan cña biÕn ®−îc chØ ra bëi tªn biÕn víi c¸c biÕn ®−îc trong danh s¸ch
biÕn
VÝ dô:
. pwcorr poor hhsize rlpcex1 sex
| poor hhsize rlpcex1 sex
-------------+------------------------------------
poor | 1.0000
hhsize | 0.2425 1.0000
rlpcex1 | -0.4452 -0.2172 1.0000
sex | -0.1028 -0.2570 0.1267 1.0000
2.2. Ph©n tÝch håi quy
Ph−¬ng ph¸p b×nh ph−¬ng nhá nhÊt (Ordinary-Least Square)
Có ph¸p:
regress <biÕn phô thuéc> [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, option]
LÖnh n y −íc l−îng c¸c hÖ sè cña h m biÕn phô thuéc (dependent variable) theo c¸c biÕn ®éc lËp
(danh s¸ch biÕn) theo ph−¬ng ph¸p b×nh ph−¬ng nhá nhÊt.
VÝ dô:](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-51-320.jpg)
![52
. reg rlpcex1 reg7 sex hhsize
Source | SS df MS Number of obs = 5999
-------------+------------------------------ F( 3, 5995) = 194.88
Model | 3.8639e+09 3 1.2880e+09 Prob > F = 0.0000
Residual | 3.9621e+10 5995 6609032.15 R-squared = 0.0889
-------------+------------------------------ Adj R-squared = 0.0884
Total | 4.3485e+10 5998 7249918.40 Root MSE = 2570.8
------------------------------------------------------------------------------
rlpcex1 | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
reg7 | 240.9633 15.5905 15.46 0.000 210.4003 271.5263
sex | 403.2984 77.38324 5.21 0.000 251.5994 554.9974
hhsize | -305.6382 17.70692 -17.26 0.000 -340.3501 -270.9263
_cons | 3160.201 155.6576 20.30 0.000 2855.056 3465.346
------------------------------------------------------------------------------
C¸c tuú chän:
level(#) ChØ ra møc tin cËy cho −íc l−îng kho¶ng tin cËy cña hÖ sè
noconstant Kh«ng cã hÖ sè (intercept) trong h m håi quy
noheader ChØ hiÓn thÞ kÕt qu¶ ph©n tÝch vÒ c¸c hÖ sè
beta HiÓn thÞ hÖ sè ®−îc chuÈn ho¸, dïng ®Ó so s¸nh møc ®é ¶nh h−ëng cña c¸c hÖ
sè víi nhau
Ph−¬ng ph¸p kh¶ n¨ng lín nhÊt (Maximum-Likelihood)
Có ph¸p:
probit <biÕn phô thuéc> [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, tuú chän]
LÖnh n y thùc hiÖn håi quy biÕn phô thuéc theo c¸c biÕn ®−îc chØ ra trong danh s¸ch biÕn theo ph−¬ng
ph¸p kh¶ n¨ng lín nhÊt. BiÕn phô thuéc th−êng l biÕn gi¶ víi hai gi¸ trÞ 0 v 1.
VÝ dô:
. probit poor reg7 sex hhsize
Iteration 0: log likelihood = -3645.1363
Iteration 1: log likelihood = -3367.2185
Iteration 2: log likelihood = -3364.8032
Iteration 3: log likelihood = -3364.8025
Probit estimates Number of obs = 5999
LR chi2(3) = 560.67
Prob > chi2 = 0.0000
Log likelihood = -3364.8025 Pseudo R2 = 0.0769
------------------------------------------------------------------------------
poor | Coef. Std. Err. z P>|z| [95% Conf. Interval]
-------------+----------------------------------------------------------------
reg7 | -.116342 .0084551 -13.76 0.000 -.1329136 -.0997703
sex | -.1284525 .0422247 -3.04 0.002 -.2112113 -.0456937
hhsize | .1808115 .0095806 18.87 0.000 .1620338 .1995892
_cons | -.8088731 .0824798 -9.81 0.000 -.9705306 -.6472157
------------------------------------------------------------------------------](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-52-320.jpg)
![53
¦íc l−îng gi¸ trÞ biÕn phô thuéc v phÇn d−
Có ph¸p:
predict <tªn biÕn míi> [®iÒu kiÖn] [ph¹m vi] [, xb stdp resid]
LÖnh n y ®−îc thùc hiÖn sau lÖnh regress (hoÆc probit) ®Ó t¹o ra 1 biÕn míi cã gi¸ trÞ ®−îc tÝnh tuú
theo tuú chän ®−îc chØ ra.
C¸c tuú chän:
xb cho phÐp −íc l−îng gi¸ trÞ cña biÕn phô thuéc thu ®−îc tõ h m håi quy:
i10i XˆˆYˆ β+β=
stdp −íc l−îng sai sè chuÈn cña gia trÞ −íc l−îng:
),(CovX2)ˆ(VarX)(VarSE 10i1
2
i0i ββ−β+β=
redid −íc l−îng gi¸ trÞ phÇn d−:
iii YˆYe −=
VÝ dô:
predict exphat, xb
T¹o ra biÕn míi exphat cã gi¸ trÞ −íc l−îng cña biÕn phô thuéc (fitted value) theo hÖ sè thu ®−îc tõ
h m håi quy.
predict expres, resid
T¹o ra biÕn expres cã gi¸ trÞ cña phÇn d−.
KiÓm ®Þnh vÒ hÖ sè cña h m håi quy
Có ph¸p:
test [gi¸ trÞ biÓu thøc]
test [danh s¸ch biÕn]
testparm <danh s¸ch biÕn> [, equal ]
LÖnh test kiÓm ®Þnh c¸c gi¶ thiÕt vÒ hÖ sè cña h m håi quy võa míi ®−îc −íc l−îng
VÝ dô:
test urban98 =2000
KiÓm ®Þnh gi¶ thiÕt hÖ sè cña biÕn urban98 = 0
test region1 = region2
KiÓm ®Þnh gi¶ thiÕt hÖ sè cña biÕn region1 b»ng hÖ sè cña biÕn region2
test region1 = (region2+region3)/2
KiÓm ®Þnh gi¶ thiÕt vÒ quan hÖ gi÷a c¸c hÖ sè cña biÕn region1, region2, va region3
test region1 region2 region3](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-53-320.jpg)
![54
KiÓm ®Þnh gi¶ thiÕt hÖ sè cña biÕn region1, region2, va region3 ®Òu b»ng 0
testparm region*
KiÓm ®Þnh gi¶ thiÕt vÒ cña hÖ sè cña biÕn region1 ®Õn region7 ®Òu b»ng 0
. tab reg7, gen(region)
Code by 7 |
regions | Freq. Percent Cum.
------------+-----------------------------------
region1 | 859 14.32 14.32
region2 | 1175 19.59 33.91
region3 | 708 11.80 45.71
region4 | 754 12.57 58.28
region5 | 368 6.13 64.41
region6 | 1023 17.05 81.46
region7 | 1112 18.54 100.00
------------+-----------------------------------
Total | 5999 100.00
. reg rlpcex1 urban98 region* sex educyr98 hhsize
Source | SS df MS Number of obs = 5999
-------------+------------------------------ F( 10, 5988) = 382.87
Model | 1.6960e+10 10 1.6960e+09 Prob > F = 0.0000
Residual | 2.6525e+10 5988 4429712.49 R-squared = 0.3900
-------------+------------------------------ Adj R-squared = 0.3890
Total | 4.3485e+10 5998 7249918.40 Root MSE = 2104.7
------------------------------------------------------------------------------
rlpcex1 | Coef. Std. Err. t P>|t| [95% Conf. Interval]
-------------+----------------------------------------------------------------
urban98 | 1995.163 66.46943 30.02 0.000 1864.859 2125.467
region1 | -923.7066 132.8334 -6.95 0.000 -1184.108 -663.3052
region2 | -362.6047 130.2254 -2.78 0.005 -617.8934 -107.316
region3 | -558.0354 137.1551 -4.07 0.000 -826.9089 -289.1619
region4 | -100.7586 135.8372 -0.74 0.458 -367.0486 165.5313
region5 | (dropped)
region6 | 1742.688 131.9928 13.20 0.000 1483.934 2001.441
region7 | 151.9854 128.0272 1.19 0.235 -98.99396 402.9648
sex | 270.9142 66.61031 4.07 0.000 140.3339 401.4944
educyr98 | 153.3281 6.836934 22.43 0.000 139.9253 166.731
hhsize | -257.691 14.73741 -17.49 0.000 -286.5816 -228.8004
_cons | 2362.355 178.3197 13.25 0.000 2012.784 2711.926
------------------------------------------------------------------------------
. test urban98 =2000
( 1) urban98 = 2000.0
F( 1, 5988) = 0.01
Prob > F = 0.9420
. test region1 = region2
( 1) region1 - region2 = 0.0
F( 1, 5988) = 34.57](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-54-320.jpg)
![56
graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, lo¹i_®å_thÞ tuú_chän_riªng
tuú_chän_chung]
Trong ®ã:
lo¹i_®å_thÞ (graph_type) ChØ ra lo¹i ®å thÞ cÇn vÏ
tuú_chän_riªng (specific_options) C¸c tuú chän liªn quan ®Õn tõng lo¹i ®å thÞ
tuú_chän_chung (common_options) C¸c tuú chän cã thÓ sö dông chung cho c¸c lo¹i ®å thÞ nh− tuú
chän vÒ ®¸nh nh n trªn c¸c trôc cña ®å thÞ
Stata cho phÐp vÏ 8 lo¹i ®å thÞ nh− sau (graph_type):
(1) §å thÞ 2 chiÒu (two-way scatterplots)
. graph rlpcex1 age
comp.M&Regpriceadj.pctotexp
Age of household head
16 95
357.318
45801.7
(2) Ma trËn ®å thÞ 2 chiÒu (two-way scatterplot matrices)
. gr rlpcex1 age educyr98 hhsize, matrix](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-56-320.jpg)
![63
* HiÓn thÞ gi¸ trÞ trôc ®å thÞ
xlabel[(gi¸ trÞ sè)] ylabel[(gi¸ trÞ sè)] rlabel[(gi¸ trÞ sè)] tlabel[(gi¸ trÞ sè)]
VÝ dô:
gr meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr
dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel
Chitieubinhquan(trdong)
Sonamhoccuachuho
Do thi chi tieu va hoc van chu ho
Quy mo ho gia dinh
Chi tieu binh quan So nam hoc
0 5 10 15 20
2
4
6
8
Chó ý: C¸c lùa chän kh¸c cã thÓ xem ë phÇn help b»ng lÖnh: help graxes
C¸c tuú chän vÒ ®−êng nèi
xline[(gi¸ trÞ sè)] yline[(gi¸ trÞ sè)] rline[(gi¸ trÞ sè)] tline[(gi¸ trÞ sè)]
connect(c[[p]] ... c[[p]])
VÝ dô:
. gr meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr
dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel xline (5 10 to 20)
yline(2 4 to 8) connect(ll)](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-63-320.jpg)
![64
Chitieubinhquan(trdong)
Sonamhoccuachuho
Do thi chi tieu va hoc van chu ho
Quy mo ho gia dinh
Chi tieu binh quan So nam hoc
0 5 10 15 20
2
4
6
8
2. Mét sè lo¹i ®å thÞ th−êng dïng
2.1. §å thÞ 2 chiÒu
Có ph¸p:
graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], twoway [tuú_chän_chung rescale]
Tuú chän rescale cho phÐp hiÖn thÞ hai trôc tung víi gi¸ trÞ kh¸c nhau
. gen meanexp1=meanexp*1000
. label var meanexp1 "Chi tieu binh quan"
. gr meanexp1 meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan
(nghin dong)) b2title (Quy mo ho gia dinh) xlabel ylabel rlabel(2 4 to 8) connect(ll) rescale](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-64-320.jpg)
![65
Chitieubinhquan(nghindong)
Do thi chi tieu va hoc van chu ho
Quy mo ho gia dinh
Sonamhoc
Chi tieu binh quan So nam hoc
0 5 10 15 20
1000
2000
3000
4000
5000
2
4
6
8
2.2. §å thÞ tÇn suÊt
Có ph¸p:
graph [biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], histogram [tuú_chän_chung bin(#) freq
normal[(#,#)] density(#)]
C¸c tuú chän:
bin(#) ChØ ra sè l−îng kho¶ng cho ®å thÞ, gi¸ trÞ ngÇm ®Þnh l bin(5)
Freq Gi¸ trÞ tÇn suÊt sÏ ®−îc hiÓn thÞ trªn trôc tung
normal[(#,#)] VÏ h m ph©n phèi chuÈn
density(#)] §−îc dïng víi lùa chän normal, chØ ra sè l−îng ®iÓm ®Ó −íc l−îng
h m mËt ®é theo ph©n phèi chuÈn
VÝ dô:
§å thÞ tÇn suÊt cña chi tiªu binh qu©n ®Çu ng−êi
. gr rlpcex1, hist bin(20) normal](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-65-320.jpg)
![67
Frequency
Histograms by Code by 7 regions
comp.M&Reg price adj.pc tot exp
region1
0
415
region2 region3
region4
0
415
region5
357.318 45801.7
region6
357.318 45801.7
region7
357.318 45801.7
0
415
2.3. §å thÞ h×nh cét
Có ph¸p:
graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], bar [tuú_chän_chung [no]alt means
stack]
VÝ dô:
§å thÞ gi¸ trÞ trung b×nh häc vÊn cña chñ hé v quy m« hé gia ®×nh theo 7 vïng
. gr educyr98 hhsize, bar means by(reg7)
0
8.64426
schooling year of HH.head Household size
1 2 3 4 5 6 7
. label define region 1 "region1" 2 "region2" 3 "region3" 4 "region4" 5 "region5" 6 "region6" 7
"region7"](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-67-320.jpg)
![69
0
500
1000
1500
persons 1:urban 98; 0:rural 98
region1
region2
region3
region4
region5
region6
region7
VÝ dô:
H y vÔ ®å thÞ sau:
0
200
400
600
foodpoor poor
region1
region2
region3
region4
region5
region6
region7
2.4. §å thÞ h×nh trßn
Có ph¸p:
graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], pie [tuú_chän_chung]
LÖnh n y vÏ ®å thÞ h×nh trßn Mèi biÕn sÏ chiÕm 1 phÇn cña h×nh trßn v tû lÖ cña phÇn n y do tæng gi¸
trÞ cña c¸c quan s¸t cu¶ biÕn ®ã quyÕt ®Þnh.
VÝ dô:
VÏ ®å thÞ tû lÖ phÇn tr¨m sè ng−êi nghÌo cña mçi vïng trªn tæng sè ng−êi nghÌo cña c¶ n−íc.
. gr poor1-poor7, pie](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-69-320.jpg)
![71
12% foodpoor
18% poor but still above food povert
70% nonpoor
region1 region2 region3
region4 region5 region6
region7 Total
3. L−u tr÷ v hiÓn thÞ ®å thÞ (Saving and graph using)
§Ó l−u tr÷ ®å thÞ th× t¹i cöa sæ graph, v o thùc ®¬n File, chän Save graph, sau ®ã lùa chän ®−êng dÉn
v tªn file cho ®å thÞ, phÇn më réng ngÇm ®Þnh l gph.
§å thÞ còng cã thÓ ®−îc l−u tr÷ b»ng tuú chän saving(tªn tÖp [,replace]) viÕt sau lÖnh graph
VÝ dô:
. gr educyr98 hhsize, bar means by(reg7) ylabel( 2 4 to 10) alt saving ("c: do thi 1")
. gr persons urban98, bar ylabel by(reg7) stack alt saving("c:do thi 2")
§Ó kh«ng hiÓn thÞ ®å thÞ th× cã thÓ dïng lÖnh t¾t chÕ ®é hiÓn thÞ ®å thÞ b»ng lÖnh
set graphics { on | off }
. set graphics off
. gr poor1-poor7, pie saving ("c:do thi 3", replace)
(note: file c:do thi 3.gph not found)
Stata cho phÐp hiÓn thÞ c¸c ®å thÞ ® l−u tr÷ b»ng lÖnh:
graph using <tÖp tÖp ®å thÞ 1> [tÖp tÖp ®å thÞ 2 ...] [, margin(#)]
margin(#) chØ ra kho¶ng c¸ch lÒ bao quanh ®å thÞ theo gi¸ trÞ phÇn tr¨m cña diÖn tÝch ®å thÞ. Gi¸ trÞ
ngÇm ®Þnh l 0.
VÝ dô:
. set graphics on](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-71-320.jpg)
![73
Ch−¬ng V: LËp tr×nh trong Stata
1. Giíi thiÖu chung vÒ ch−¬ng tr×nh do-file
1.1. Më v l−u tr÷ do-file
Stata cho phÐp viÕt c¸c tÖp ®−îc gäi l do-file bao gåm c¸c lÖnh cña Stata. Thay v× thùc hiÖn tõng lÖnh
mét tõ cöa sæ lÖnh command, c¸c tÖp do-file sÏ lÇn l−ît thùc hiÖn c¸c lÖnh ®ã.
Ch−¬ng tr×nh Stata ®−îc so¹n th¶o trong cöa sæ do-file editor. Cöa sæ n y ®−îc më b»ng c¸ch kÝch v o
thùc ®¬n Windows v chän tuú chän do-file editor. Mét c¸ch kh¸c ®Ó më cöa sæ n y l gâ lÖnh doedit
t¹i cöa sæ lÖnh command.
VÝ dô:
Mét ch−¬ng tr×nh cã thÓ ®−îc so¹n th¶o trong cöa sæ do-file editor nh− sau:
----------------
clear
set mem 32m
use "C:VLSS98Hhexp98n.dta", clear
tab urban98
sum hhsize
gen new=hhsizet
gen new=hhsize
----------------
Sau khi so¹n th¶o, do-file sÏ ®−îc l−u tr÷ b»ng tuú chän Save as trong thùc ®¬n File cña cöa sæ do-file
editor. Tªn cña do-file cã thÓ ®−îc chØ ra ngay t¹i lÖnh doedit nh− sau:
doedit (tªn do-file)
TÖp do-file cã phÇn më réng l do.
ë vÝ dô trªn chóng ta cã thÓ l−u tr÷ ®o¹n ch−¬ng tr×nh d−íi tªn l “ch−¬ng tr×nh 1” t¹i th− môc Vlss98
trªn æ ®Üa C.
1.2. Thùc hiÖn c¸c tÖp do-file
§Ó ch¹y do-file th× t¹i cöa sæ lÖnh chóng ta gâ mét trong hai lÖnh sau:
do filename [, nostop]
run filename [, nostop]
LÖnh run thùc hiÖn c¸c lÖnh trong do-file nh−ng kh«ng hiÓn thÞ kÕt qu¶ ra m n h×nh.
Trong qu¸ tr×nh thùc hiÖn do-file, nÕu cã c©u lÖnh sai th× Stata sÏ b¸o lçi v ngõng viÖc thùc hiÖn c¸c
c©u lÖnh sau ®ã. Tuy nhiªn nÕu tuú chän nostop ®−îc chØ ra th× Stata sÏ bá qua c©u lÖnh bÞ lçi v tiÕp
tôc thùc hiÖn c¸c lÖnh sau c©u lÖnh lçi ®ã.
VÝ dô:](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-73-320.jpg)
![75
------------+-----------------------------------
Rural | 4269 71.16 71.16
Urban | 1730 28.84 100.00
------------+-----------------------------------
Total | 5999 100.00
. sum hhsize
Variable | Obs Mean Std. Dev. Min Max
-------------+-----------------------------------------------------
hhsize | 5999 4.752292 1.954292 1 19
. gen new=hhsizet
hhsizet not found
r(111);
. gen new=hhsize
. end of do-file
Thùc hiÖn (ch¹y) b»ng lÖnh run
. run "c:vlss98chuong trinh 1", nostop
hhsizet not found
C¸c do-file cã thÓ thùc hiÖn b»ng tuú chän Do trong thùc ®¬n File, hoÆc thùc hiÖn trùc tiÕp trong cöa
sæ Do-file editor b»ng tuú chän Do hoÆc Run trong thùc ®¬n Tool.
1.3. Mét sè l−u ý khi so¹n th¶o do-file
version #
Khi so¹n th¶o c¸c tÖp do-file chóng ta nªn ®−a dßng lÖnh n y v o ®Çu ch−¬ng tr×nh ®Ó th«ng b¸o phiªn
b¶n Stata ®−îc dïng ®Ó so¹n th¶o do-file. VÝ dô nÕu nh− chóng ta dïng Stata 7.0 ®Ó so¹n th¶o do-file
th× c©u lÖnh n y sÏ ®−îc ®−a v o ®Çu ch−¬ng tr×nh nh− sau:
version 7.0
clear
use Hhexp98n.dta
tab reg7
….
C¸c phiªn b¶n Stata kh¸c nhau sÏ cã thÓ cã sù kh¸c nhau vÒ có ph¸p hoÆc ý nghÜa cña c¸c c©u lÖnh.
LÖnh version cho phÐp ch−¬ng tr×nh Stata ch¹y cã thÓ hiÓu ®óng ®−îc néi dung cña tÖp do-file ®−îc
viÕt bëi c¸c phiªn b¶n kh¸c.
set memory #[k|m]](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-75-320.jpg)
![80
. macro list _a
local macro `a' not found
r(111);
Trong khi ®ã ®èi víi global macros
. do "C:WINDOWSTEMPSTD010000.tmp"
. global b "chuong trinh thong ke Stata"
. end of do-file
. macro list b
b: chuong trinh thong ke Stata
3. TÝch v« h−íng v ma trËn (scalar and matrix)
3.1. Ma trËn (matrix)
Stata ®Þnh nghÜa ma trËn A[r, c] l mét m¶ng h×nh ch÷ nhËt gåm r h ng (row) v c cét (column).
VÝ dô:
NÕu ma trËn A ® ®−îc t¹o ra th× chóng ta cã thÓ xem néi dung cña ma trËn ®ã nh− sau:
. matrix list A
A[3,3]
c1 c2 c3
r1 1 2 4
r2 3 4 7
r3 10 11 14
ë ®©y ma trËn A bao gåm 9 phÇn tö (element): 1, 2, 4, 3, 4, 7, 10, 11, 14. C¸c cét ®−îc ®Æt tªn l c1,
c2, v c3, v c¸c h ng l r1, r2, v r3. PhÇn tö l giao ®iÓm cña dßng 1 v cét 2 ®−îc ký hiÖu l A[1, 2].
Trong vÝ dô n y A[1, 2] chøa gi¸ trÞ b»ng 2.
3.2. TÝch v« h−íng (scalar)
TÝch v« h−íng chøa 1 phÇn tö l sè. TÝch v« h−íng ®−îc ®Þnh nghÜa b»ng lÖnh sau:
scalar scalar_name = expression
VÝ dô:
. scalar a = 10
. scalar list a
a = 10
. scalar b = a* 2
. scalar list b
b = 20](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-80-320.jpg)
![81
Trong chõng mùc n o ®ã, tÝch v« h−íng cã thÓ xem nh− mét tr−êng hîp ®Æc biÖt cña ma trËn chØ cã 1
ph©n tö (mét h ng v mét cét).
3.3. Mét sè lÖnh l m viÖc víi ma trËn
ThiÓt lËp kÝch th−íc ma trËn
Gia trÞ ngÇm ®Þnh cña kÝch th−íc ma trËn l tèi ®a 40 h ng v 40 cét. Chóng ta cã thÓ thay ®æi kÝch
th−íc tèi ®a n y b»ng lÖnh:
. set matsize 500
LÖnh n y cho phÐp c¸c ma trËn ®−îc t¹o ra cã thÓ bao gåm 500 h ng v 500 cét.
T¹o ma trËn
Ma trËn cã thÓ t¹o ra b»ng c¸c c©u lÖnh trùc tiÕp.
VÝ dô:
matrix mymat = (1,23,4) C¸c phÇn tö ®−îc ph©n biÖt bëi dÊu phÈy, cßn c¸c h ng ®−îc
ph©n biÖt bëi dÊu g¹ch chÐo
matrix myvec = (1 5 3 1 3) T¹o ra vÐct¬ h ng
matrix mycol = (1/5/3/1/3) T¹o ra vÐct¬ cét
Ma trËn còng cã thÓ ®−îc t¹o ra tõ sè liÖu b»ng lÖnh:
mkmat <danh s¸ch biÕn> [®iÒu kiÖn] [ph¹m vi] [, matrix(tªn ma trËn) ]
VÝ dô:
. input maho quymo thunhap
maho quymo thunhap
1. 101 6 1200
2. 103 5 1400
3. 105 5 3200
4. 107 9 1000
5. 109 4 2500
6. end
. mkmat maho quymo thunhap, matrix(A)
. matrix list A
A[5,3]
maho quymo thunhap
r1 101 6 1200
r2 103 5 1400
r3 105 5 3200
r4 107 9 1000](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-81-320.jpg)
![83
commands 1
}
else {
comands 2
}
- C¸c lÖnh if…else cã thÓ ®−îc sö dông lång víi nhau
®iÒu kiÖn (®iÓu kiÖn) {
Nhãm c©u lÖnh 1
}
else ®iÒu kiÖn (®iÒu kiÖn) {
….
4.2. LÖnh while
Có ph¸p:
while <®iÒu kiÖn logic> {
Nhãm c©u lÖnh
}
Stata sÏ kiÓm tra ®iÒu kiÖn logic (expression), nÕu ®iÒu kiÖn n y ®óng th× c¸c lÖnh ë “Nhãm c©u lÖnh”
sÏ ®−îc thùc hiÖn, nÕu ®iÒu kiÖn sai th× c¸c lÖnh n y sÏ kh«ng ®−îc thùc hiÖn.
VÝ dô:
local i=1
while `i’<= 10 {
if mod(`i',2) {
display "`i' is odd"
}
else {
display "`i' is even"
}
local i=`i’+1
}
Chó ý:
Vßng lÆp cã thÓ ®−îc dõng l¹i nÕu sö dông tuú chän sau ®©y ë gi÷a vßng lÆp:
continue [, break]
NÕu gÆp lÖnh continue, Stata sÏ bá qua c¸c lÖnh ë sau ®ã v quay l¹i lÖnh ®Çu tiªn cña vßng lÆp. NÕu
c¶ tuú chän break ®−îc chØ ra th× Stata sÏ tho¸t khái vßng lÆp.](https://image.slidesharecdn.com/huongdansudungstata8-140708051541-phpapp02/85/H-ng-d-n-s-d-ng-STATA-83-320.jpg)
Hướng dẫn sử dụng STATA
- 1. 1 Sö dông ch−¬ngtr×nh Stata 8 néi dung Ch−¬ng I: Giíi thiÖu chung vÒ ch−¬ng tr×nh Stata .................................................................. 2 1. Tæ chøc l−u tr÷ d÷ liÖu trong Stata (Dataset in Stata)..........................................................2 2. Khëi ®éng v tho¸t khái Stata (Open and exit) ...................................................................3 3. Giao diÖn Stata 7 (Stata interface).......................................................................................3 4. Biªn b¶n l m viÖc (log file)............................................... Error! Bookmark not defined. 5. NhËp v l−u d÷ liÖu (Use, input and and save)....................................................................6 Ch−¬ng II: Khai th¸c d÷ liÖu...................................................................................................... 8 1. CÊu tróc lÖnh trong Stata (Stata command syntax)..............................................................8 2.To¸n tö v h m sè (Operators and functions) ....................................................................11 3. M« t¶ d÷ liÖu (Data reporting)...........................................................................................12 4. Biªn tËp v söa ch÷a d÷ liÖu (Data manipulation).............................................................25 5. QuyÒn sè trong VHLSS (Weight)......................................................................................38 Ch−¬ng III: KiÓm ®Þnh gi¶ thiÕt v ph©n tÝch håi quy........................................................... 43 1. ¦íc l−îng v kiÓm ®Þnh gi¶ thiÕt (Estimation and hypothesis testing).............................43 2. Ph©n tÝch t−¬ng quan v håi quy (Correlation and regression) ........................................49 Ch−¬ng IV: VÏ ®å thÞ................................................................................................................ 55 1. VÏ ®å thÞ (graph)...............................................................................................................55 2. Mét sè lo¹i ®å thÞ th−êng dïng .........................................................................................64 3. L−u tr÷ v hiÓn thÞ ®å thÞ (Saving and graph using)..........................................................71 Ch−¬ng V: LËp tr×nh trong Stata ............................................................................................ 73 1. Giíi thiÖu chung vÒ ch−¬ng tr×nh do-file ..........................................................................73 2. Local v global macros .....................................................................................................77 3. TÝch v« h−íng v ma trËn (scalar and matrix)...................................................................80 4. LÖnh ®iÒu kiÖn v vßng lÆp ...............................................................................................82 5. Giíi thiÖu vÒ file ado.........................................................................................................84 T i liÖu tham kh¶o..................................................................................................................... 85 Phô lôc........................................................................................................................................ 85
- 2. 2 Ch−¬ng I: GiíithiÖu chung vÒ ch−¬ng tr×nh Stata 8 1. Tæ chøc l−u tr÷ d÷ liÖu trong Stata (Dataset in Stata) Stata l phÇn mÒm thèng kª sö dông ®Ó qu¶n lý, ph©n tÝch sè liÖu v vÏ ®å thÞ. Stata cho phÐp l−u tr÷ th«ng tin vÒ c¸c ®Æc ®iÓm cña c¸c ®èi t−îng nghiªn cøu. Sè liÖu l−u tr÷ trong Stata cã thÓ ®−îc hiÓn thÞ d−íi d¹ng b¶ng nh− vÝ dô sau: maho tenchuho quymoho thunhapbq 101 Nguyen Van A 6 2100 102 Le Thi B 5 3210 103 Tran Van C 10 1200 Quan s¸t (observation) Mçi mét h ng ngang cña b¶ng sè liÖu ®−îc gäi l mét quan s¸t, hay mét b¶n ghi (record) l−u tr÷ sè liÖu vÒ mét ®èi t−îng nghiªn cøu. ë vÝ dô trªn cã 3 quan s¸t l−u tr÷ sè liÖu vÒ M hé (maho); Tªn chñ hé (tenchuho); Quy m« hé (quymoho); Thu nhËp b×nh qu©n (thunhapbq) cña 3 hé gia ®×nh. BiÕn (variable) Th«ng tin vÒ ®èi t−îng nghiªn cøu ®−îc thu thËp v l−u tr÷ theo c¸c ®Æc ®iÓm cña chóng. C¸c ®Æc ®iÓm n y ®−îc gäi l biÕn. BiÕn ®−îc xem l c¸c cét cña b¶ng sè liÖu. ë vÝ dô trªn cã 4 biÕn, víi tªn l maho, tenchuho, quymoho, v thunhapbq. Tªn biÕn d i tõ 1 ®Õn 32 ký tù, ®−îc b¾t ®Çu ch÷ hoÆc dÊu g¹ch d−íi (_). Tªn biÕn chØ bao gåm ch÷, sç v dÊu g¹ch d−íi. C¸c ký tù ®Æc biÖt kh¸c kh«ng thÓ dïng ®Ó ®Æt tªn cho biÕn. BiÕn x¸c ®Þnh (identifying variables) Th«ng th−êng trong c¸c biÕn sÏ cã c¸c biÕn dïng ®Ó nhËn d¹ng quan s¸t, ®−îc gäi l biÕn x¸c ®Þnh. Nhê cã c¸c biÕn x¸c ®Þnh n y m c¸c quan s¸t cã thÓ ph©n biÖt ®−îc víi nhau. Mçi mét quan s¸t cã mét gi¸ trÞ cña c¸c biÕn n y. ë vÝ dô trªn, biÕn x¸c ®Þnh l maho, ®èi víi mçi mét quan s¸t biÕn maho nhËn mét gi¸ trÞ. C¸c ®Æc ®iÓm cña biÕn C¸c biÕn cã thÓ ®−îc g¸n nh n (chó thÝch). VÝ dô biÕn maho cã thÓ ®−îc g¸n nh n l “M hé”. BiÕn cã thÓ ®−îc ®Þnh d¹ng (format) l biÕn sè v biÕn ký tù víi c¸c lo¹i l−u tr÷ kh¸c nhau. BiÕn sè cã thÓ l−u tr÷ d−íi lo¹i byte; int; long; float; double. Cßn biÕn ký tù th× cã thÓ l−u tr÷ d−íi d¹ng str1 ®Õn str80 cho c¸c ®é d i kh¸c nhau. KiÓu l−u tr÷ d¹ng sè Dung l−îng (Byte) Gi¸ trÞ nhá nhÊt Gi¸ trÞ lín nhÊt KiÓu byte 1 -127 126 Sè nguyªn int 2 -32,767 32,766 Sè nguyªn long 4 -2,147,483,647 2,147,483,646 Sè nguyªn float 4 -10^36 10^36 Sè thùc double 8 -10^308 10^308 Sè thùc C¸c biÕn sè cã thÓ bao gåm c¸c biÕn rêi r¹c v liªn tôc. C¸c biÕn nh− l quy m« hé gia ®×nh, giíi tÝnh chñ hé, vïng ®Þa lý, tr×nh ®é gi¸o dôc l c¸c biÕn rêi r¹c (discrete) (hay cßn gäi l biÕn ph©n lo¹i
- 3. 3 (categorical)). C¸c biÕnn y cã thÓ ®−îc l−u tr÷ d−íi d¹ng byte, int, v long. C¸c biÕn liªn tôc (continuous) nh− thu nhËp, chi tiªu cña hé th× l−u tr÷ d−íi d¹ng float hoÆc double. BiÕn ký tù (string) dïng ®Ó l−u tr÷ c¸c lo¹i ký tù. VÝ dô biÕn tenchuho l biÕn kiÓu ký tù dïng ®Ó l−u tr÷ tªn cña chñ hé. KiÓu l−u tr÷ d¹ng ch÷ Byte §é d i lín nhÊt str1 1 1 str2 2 2 ... str80 80 80 2. Khëi ®éng v tho¸t khái Stata (Open and exit) Stata ®−îc khëi ®éng t−¬ng tù nh− c¸c ch−¬ng tr×nh tin häc øng dông kh¸c, b»ng c¸ch kÝch v o biÓu t−îng cña tÖp wstata.exe trong Windows explorer, hoÆc chän b»ng c¸ch chän Start -> Program -> Stata. Ch−¬ng tr×nh ®−îc tho¸t ra b»ng lÖnh exit tõ cöa sæ lÖnh Stata Command, hoÆc tuú chän exit trong thùc ®¬n (menu) File. 3. Giao diÖn Stata 8 (Stata interface)1 Sau khi Stata ®−îc khëi ®éng, giao diÖn cña Stata sÏ ®−îc hiÖn lªn, bao gåm thanh thùc ®¬n (menu bar) ë trªn cïng, d−íi ®ã l thanh c«ng cô (tool bar) v c¸c cöa sæ (windows).
- 4. 4 C¸c cöa sæcña Stata C¸c cöa sæ cña Stata ®−îc më ra b»ng viÖc lùa chän c¸c tuú chän ë thanh thùc ®¬n Windows (menu bar). C¸c cöa sæ n y bao gåm: Results HiÓn thÞ c¸c lÖnh v kÕt qu¶ Graph HiÓn thÞ ®å thÞ Viewer HiÓn thÞ cöa sæ trî gióp (help) v hiÓn thÞ néi dung c¸c file v¨n b¶n (text) Command Dïng ®Ó gâ c¸c c©u lÖnh Review HiÓn thÞ c¸c lÖnh ® thùc hiÖn Variables HiÓn thÞ danh s¸ch c¸c biÕn cña tÖp sè liÖu Data editor HiÓn thÞ v söa ch÷a sè liÖu d−íi d¹ng b¶ng Do-file editor HiÓn thÞ cöa sæ ®Ó so¹n th¶o ch−¬ng tr×nh Thanh thùc ®¬n (Menu bar) B»ng c¸ch kÝch v o thanh thùc ®¬n v c¸c tuú chän trong ®ã, Stata sÏ thùc hiÖn c¸c lÖnh kh¸c nhau. Thanh thùc ®¬n bao gåm c¸c nhãm lÖnh sau ®©y: File Open Më file sè liÖu View Xem c¸c file cña Stata trong cöa sæ Viewer Save L−u file sè liÖu Save as L−u file sè liÖu d−íi tªn míi File name Chän tªn file ®Ó ®−a v o cöa sæ lÖnh Log §ãng, më, xem l¹i log file Save graph L−u gi÷ file ®å thÞ Print graph In ®å thÞ Print results In kÕt qu¶ Exit Tho¸t khái Stata Edit Copy text Sao chÐp v¨n b¶n (text) Copy tables Sao chÐp b¶ng biÓu Paste D¸n Table copy options Lùa chän sao chÐp b¶ng sè liÖu Graph copy options Lùa chän sao chÐp ®å thÞ (kh«ng cã trong Stata 7)
- 5. 5 Prefs C¸c tuúchän vÒ m u s¾c, ph«ng ch÷, v kÝch cì Windows Results Më cöa sæ kÕt qu¶ Graph Më cöa sæ ®å thÞ Log Më cöa sæ log file Viewer Më cöa sæ trî gióp (help) v xem néi dung file Command Më cöa sæ c©u lÖnh Review Më cöa sæ c¸c lÖnh ® thùc hiÖn Variables Më cöa sæ danh s¸ch c¸c biÕn cña tÖp sè liÖu Help/Search Më cöa sæ trî gióp (help) Data editor Më cöa ®Ó xem sè liÖu l−u tr÷ d−íi d¹ng b¶ng Do-file editor Më cöa sæ viÕt ch−¬ng tr×nh Help C¸c trî gióp liªn quan ®Õn viÖc sö dông Stata Thanh c«ng cô (tool bar) C¸c tuú chän trªn thanh c«ng cô ®−îc thiÕt kÕ ®Ó thùc hiÖn c¸c lÖnh th«ng dông cña Stata. NÕu chóng ta di chuyÓn con trá ®Õn c¸c nót n y th× sÏ hiÖn lªn c¸c c©u huíng dÉn, bao gåm: Open (use) Më file sè liÖu Stata Save L−u tr÷ file sè liÖu ra ®Üa Print results In néi dung cña cöa sæ kÕt qu¶ Begin log Më, ®ãng v xem néi dung cña file log Start viewer Më cöa sæ trî trî (help) Bring Dialog Window to font §−a cöa sæ hép tho¹i ra phÝa tr−íc Bring Result Window to font §−a cöa sæ kÕt qu¶ ra phÝa tr−íc Bring Graph Window to font §−a cöa sæ vÏ ®å thÞ ra phÝa tr−íc Do-file editor Më cöa sæ so¹n th¶o ch−¬ng tr×nh Data editor Më cöa sæ söa ch÷a sè liÖu Data browser Më cöa sæ xem sè liÖu Clear –more- condition T¾t lÖnh more Break Dõng viÖc thùc hiÖn lÖnh hoÆc ch−¬ng tr×nh
- 6. 6 4. NhËp vl−u d÷ liÖu (Use, input and and save) Më tÖp sè liÖu ®ang cã: TÖp sè liÖu Stata cã thÓ ®−îc më b»ng lùa chän Open trªn thùc ®¬n File; hoÆc nót Open (use) trªn thanh c«ng cô tool bar. NÕu file sè liÖu cã dung l−îng lín th× chóng ta ph¶i thiÕt lËp bé nhí cÇn dïng cho Stata b»ng lÖnh: set memory #[k|m] VÝ dô: set mem 32m set mem 32000k NhËp sè liÖu Cã mét sè c¸ch ®Ó nhËp sè liÖu tõ b n phÝm v o bé nhí cña Stata. - Sö dông cöa sæ Stata editor ®Ó nhËp sè liÖu. HoÆc tõ cöa sæ command, gâ lÖnh edit. Sau ®ã nhËp sè liÖu theo kiÓu biÓu b¶ng trong cöa sæ n y.
- 7. 7 Stata cho phÐpnhËp sè liÖu tõ c¸c file c¬ së d÷ liÖu kh¸c. Tr−íc hÕt c¸c file sè liÖu n y cÇn ®−îc l−u tr÷ d−íi d¹ng text (cã thÓ b»ng ch−¬ng tr×nh Excel), c¸c quan s¸t ®−îc c¸c nhau 1 dßng v c¸c gi¸ trÞ c¸ch nhau 1 dÉu phÈy (commas) hoÆc dÊu c¸ch (tab). Sau ®ã dïng lÖnh copy v paste ®Ó nhËp sè liÖu n y v o Stata. L−u tr÷ sè liÖu ViÖc l−u tr÷ sè liÖu cã thÓ thùc hiÖn b»ng c¸c tïy chän Save v Save as ë trong thanh thùc ®¬n (menu bar); hoÆc nót Save trªn thanh c«ng cô (tool bar). Chó ý: Xem thªm lÖnh infile v outfile
- 8. 8 Ch−¬ng II: Khaith¸c d÷ liÖu 1. CÊu tróc lÖnh trong Stata (Stata command syntax) CÊu tróc c¬ b¶n cña mét lÖnh trong Stata nh− sau: [by danh s¸ch biÕn:] Có ph¸p lÖnh [danh s¸ch biÕn] [biÓu thøc] [®iÒu kiÖn] [ph¹m vi] [quyÒn sè] [, tuú chän] Trong phÇn H−íng dÉn s− dông (Help) cña Stata, có ph¸p lÖnh tr×nh b y b»ng tiÕng Anh nh− sau: [by varlist:] command [varlist] [=exp] [if exp] [in range] [weight] [, options] Trong ®ã dÊu ngoÆc vu«ng ký hiÖu c¸c tuú chän. Chó ý: - C¸c c©u lÖnh Stata ®−îc viÕt b»ng ch÷ th−êng. - §èi víi tªn biÕn, Stata ph©n biÖt ch÷ viÕt th−êng víi ch÷ viÕt hoa. VÝ dô, trong cïng mét tÖp sè liÖu, biÕn “Ho_ten” v biÕn “ho_ten” l 2 biÕn kh¸c nhau. - C¸c tuú chän ®−îc ký hiÖu trong dÊu ngoÆc vu«ng [ ]. C¸c tuú chän n y cã thÓ cã hoÆc kh«ng trong c©u lÖnh. C¸c tham sè b¾t buéc (tªn biÕn) ®−îc ®Æt trong dÊu ngoÆc < >. C¸c c©u lÖnh sÏ kh«ng thùc hiÖn ®−îc nÕu c¸c tham sè b¾t buéc n y kh«ng ®−îc khai b¸o. - Mét sè lÖnh Stata cho phÐp viÕt t¾t. VÝ dô lÖnh summarize cã thÓ viÕt t¾t l sum. Trong cuèn t i liÖu n y phÇn g¹ch ch©n d−íi có ph¸p cña c©u lÖnh l có ph¸p “viÕt t¾t” cña c©u lÖnh ®ã. - C¸c vÝ dô trong cuèn t i liÖu n y sö dông sè liÖu §iÒu tra Møc sèng d©n c− n¨m 1998 do Tæng côc Thèng kª tiÕn h nh. Trong ®ã TÖp chi tiªu tæng hîp Hhexp98n.dta th−êng xuyªn ®−îc sö dông. by danh s¸ch biÕn (by varlist): Stata sÏ thùc hiÖn c©u lÖnh víi theo tõng gi¸ trÞ ®−îc chØ ra bëi danh s¸ch biÕn. BiÕn ®−îc chØ ra bëi danh s¸ch biÕn ®−îc yªu cÇu s½p xÕp tr−íc khi thùc hiÖn lÖnh. VÝ dô: . sort sex . by sex: sum rlpcex1 -> sex = 1 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- rlpcex1 | 4375 2980.906 2430.648 357.318 45801.71 -> sex = 2 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- rlpcex1 | 1624 3748.368 3231.241 376.9805 30624.77
- 9. 9 Dïng thanh c«ngcô menu bar Danh s¸ch biÕn (varlist) ChØ ra danh s¸ch c¸c biÕn chÞu t¸c ®éng cña c©u lÖnh. NÕu nh− kh«ng cã biÕn n o ®−îc chØ ra th× lÖnh Stata sÏ cã t¸c dông lªn tÊt c¶ c¸c biÕn (all variables) VÝ dô: . sum hhsize sex reg7 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- hhsize | 5999 4.752292 1.954292 1 19 sex | 5999 1.270712 .4443645 1 2 reg7 | 5999 4.01917 2.145305 1 7 . sum Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- househol | 5999 19617.86 11201.92 101 38820 year | 5999 97.94666 .2247337 97 98 month | 5999 6.340723 3.011082 1 12
- 10. 10 LÖnh sum ny hiÓn thÞ thèng kª c¬ b¶n cña tÊt c¶ c¸c biÕn trong tÖp sè liÖu. §iÒu kiÖn (if exp) Stata chØ thùc hiÖn c©u lÖnh ®èi víi c¸c quan s¸t m gi¸ trÞ cña nã cho kÕt qu¶ cña biÓu thøc l ®óng. VÝ dô: . sum poor if reg7==1 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- poor | 859 .4982538 .5002882 0 1 LÖnh n y chØ cã t¸c dông ®èi víi c¸c quan s¸t m biÕn reg7 cã gi¸ trÞ b»ng 1. Ph¹m vi (in range) ChØ ra ph¹m vi c¸c quan s¸t chÞu t¸c ®éng cña c©u lÖnh. Range (ph¹m vi) cã thÓ cã c¸c d¹ng sau: sum poor in 10 TÝnh gi¸ trÞ trung b×nh cña biÕn poor cho quan s¸t 10 (chÝnh b»ng gi¸ trÞ cña biÕn poor t¹i quan s¸t thø 10) sum poor in 10/100 TÝnh gi¸ trÞ trung b×nh cña biÕn poor cho quan s¸t tõ 10 ®Õn 100 sum poor in f/100 TÝnh gi¸ trÞ trung b×nh cña biÕn poor cho quan s¸t tõ ®Çu tiªn ®Õn 100 sum poor in 100/l TÝnh gi¸ trÞ trung b×nh cña biÕn poor cho quan s¸t tõ thø 100 ®Õn quan s¸t cuèi cïng QuyÒn sè (weight) Cho phÐp tÝnh to¸n sñ dông quyÒn sè. Tuú chän vÒ quyÒn sè sÏ ®−îc tr×nh b y kü ë môc 5 cña ch−¬ng n y. C¸c tuú chän (Options) NhiÒu c©u lÖnh Stata cho phÐp c¸c tuú chän riªng. C¸c tuú chän n y ®−îc chØ ra sau dÊu phÈy. VÝ dô: LÖnh sum cã tuú chän l detail, cho phÐp tÝnh to¸n thªm mét sè thèng kª kh¸c ngo i gi¸ trÞ trung b×nh v ®é lÖnh chuÈn. . sum rlpcex1, detail comp.M&Reg price adj.pc tot exp ------------------------------------------------------------- Percentiles Smallest 1% 682.9575 357.318 5% 1012.433 366.2792 10% 1238.088 376.9805 Obs 5999 25% 1671.054 381.3502 Sum of Wgt. 5999 50% 2397.042 Mean 3188.667 Largest Std. Dev. 2692.567 75% 3711.917 26944.64 90% 5940.803 30624.77 Variance 7249918
- 11. 11 95% 8045.32 31066.5Skewness 3.791027 99% 14163.04 45801.71 Kurtosis 29.21398 Chó ý: - Stata cho phÐp viÕt t¾t c¸c lÖnh v tïy chän. Trong t i liÖu n y, phÇn g¹ch ch©n d−íi c¸c lÖnh cã nghÜa l lÖnh ®ã cã thÓ viÕt t¾t b»ng ký tù trong phÇn g¹ch ch©n n y. VÝ dô nh− lÖnh use cã nghÜa l cã thÓ ®−îc viÕt t¾t bëi u. - Có ph¸p cña c¸c c©u lÖnh trong t i liÖu n y ®−îc viÕt b»ng tiÕng Anh, cho phÐp ng−êi ®äc cã thÓ ®èi chiÕu víi phÇn h−íng dÉn sö dông trong Stata. 2.To¸n tö v h m sè (Operators and functions) C¸c to¸n tö (operators) C¸c to¸n tö trong Stata ®−îc ký hiÖu nh− sau: Ký hiÖu ý nghÜa Sè häc + Céng - Trõ * Nh©n / Chia ^ Luü thõa Quan hÖ > Lín h¬n < Nhá h¬n >= Lín h¬n hoÆc b»ng <= Nhá h¬n hoÆc b»ng == B»ng ~= Kh«ng b»ng (kh¸c) != Kh«ng b»ng (kh¸c) L«gÝc ~ Kh«ng | HoÆc & V Chó ý: Trong biÓu thøc dÊu == ®−îc dïng cho viÖc kiÓm ®Þnh biÓu thøc, vÝ dô nh− ®−îc dïng sau lÖnh if. Cßn dÊu = ®−îc dïng cho lÖnh t¹o biÕn. VÝ dô: gen RRD=0 replace RRD=1 if reg8==1
- 12. 12 C¸c h msè (function) H m sè th−êng ®−îc dïng trong biÓu thøc (exp) cña c©u lÖnh Stata. NÕu coi Y l mét h m sè cña f(X1, X2,…, Xn) th× lÖnh vÒ h m sè trong Stata sÏ tÝnh gi¸ trÞ cña Y nÕu cho c¸c gi¸ trÞ cña Xi. Stata cã 8 lo¹i h m sè: Mathematical functions Statistical functions Random numbers String functions Special functions Date functions Time-series functions Matrix functions C¸c h m to¸n häc H m thèng kª H m cho sè ngÉu nhiªn H m liªn quan ®Õn dÉy ký tù H m ®Æc biÖt H m ng y th¸ng H m chuçi thêi gian H m ma trËn VÝ dô: gen absx=abs(x) gen log_exp=log(rlpcex1) C¸c ký hiÖu cô thÓ vÒ c¸c h m sè n y cã thÓ xem ë môc help functions. 3. M« t¶ d÷ liÖu (Data reporting) 3.1. Xo¸ bé nhí cña Stata Có ph¸p: clear LÖnh n y xo¸ c¸c d÷ liÖu trong bé nhí cña Stata, b¾t ®Çu cho mét file l m viÖc míi. 3.2. H−íng dÉn sö dông lÖnh Stata Có ph¸p: help <C©u lÖnh Stata> LÖnh n y hiÓn thÞ h−íng dÉn sö dông c¸c lÖnh Stata, lÖnh Stata cÇn ph¶i ®−îc gâ ®Çy ®ñ v chÝnh x¸c. VÝ dô: . help sum help for sum not found try help contents or search sum . help summarize ----------------------------------------------------------------------------------------- help for summarize (manual: [R] summarize) ----------------------------------------------------------------------------------------- Summary statistics
- 13. 13 …. Chó ý: Chóng tacã thÓ t×m h−íng dÉn sö dông theo tõ kho¸ b»ng lÖnh search. LÖnh search cã thÓ ®−îc thùc hiÖn b»ng tuú chän Search ë thùc ®¬n help. Chóng ta còng cã thÓ dïng cöa sæ lÖnh b»ng menu bar 3.3. M« t¶ d÷ liÖu Có ph¸p: describe [danh s¸ch biÕn] LÖnh n y hiÓn thÞ th«ng tin chung nh− tªn biÕn, ®Þnh d¹ng, nh n biÕn cña c¸c biÕn ®−îc liÖt kª bëi danh s¸ch biÕn cña file sè liÖu ®ang më. NÕu nh− kh«ng cã biÕn n o ®−îc chØ ra th× lÖnh describe sÏ hiÖn thÞ th«ng tin cña tÊt c¶ c¸c biÕn. VÝ dô: . des househol year month vlssmphs storage display value variable name type format label variable label ------------------------------------------------------------------- ------------ househol long %12.0g household code
- 14. 14 year float %9.0gYear of interview month float %9.0g Month of interview vlssmphs byte %8.0g 1 if vlss, 2 if mphs source 3.4. HiÓn thÞ gi¸ trÞ cña c¸c biÕn Có ph¸p: list [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel] LÖnh n y hiÓn thÞ gi¸ trÞ cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn. Tuú chän nolable cho phÐp hiÓn thÞ gi¸ trÞ sè chø kh«ng ph¶i l gi¸ trÞ g¸n nh n. VÝ dô: . list househol farm in 1/5 househol farm 1. 36307 farm 2. 28002 farm 3. 36017 farm 4. 32418 non farm 5. 15215 non farm . list househol farm in 1/5, nolabel househol farm 1. 36307 1 2. 28002 1 3. 36017 1 4. 32418 0 5. 15215 0 3.5. Söa ch÷a, xem sè liÖu Có ph¸p: edit [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel] browse [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] [, nolabel] LÖnh edit n y më cöa sæ Data editor ®Ó ng−êi sö dông söa ch÷a, nhËp sè liÖu. Tuú chän nolable cho phÐp hiÓn thÞ gi¸ trÞ sè chø kh«ng ph¶i l gi¸ trÞ g¸n nh n. LÖnh n y cã thÓ ®−îc chän tõ tuú chän Data editor trong thanh thùc ®¬n Windows. LÖnh browse gièng lÖnh edit nh−ng kh«ng cho phÐp söa ch÷a sè liÖu. 3.6. §Õm quan s¸t Có ph¸p: count [®iÒu kiÖn] [ph¹m vi]
- 15. 15 LÖnh n y®Õm sè quan s¸t ®−îc chØ ra bëi ®iÒu kiÖn (exp) v ph¹m vi (range). NÕu ®iÒu kiÖn (exp) v ph¹m vi (range) kh«ng ®−îc chØ ra th× sÏ hiÖn thÞ sè quan s¸t cña tÖp sè liÖu. VÝ dô: . count 5999 . count if reg7==1 859 . count if reg7==1 & urban98==1 187 . count if reg7==1 & urban98==0 672 3.7. Thèng kª c¬ b¶n Có ph¸p: summarize [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, detail] LÖnh n y tÝnh to¸n v hiÓn thÞ nh÷ng thèng kª c¬ b¶n cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn. Tuú chän detail cho phÐp hiÓn thÞ thªm mét sè thèng kª nh− ®é nhän, ®é lÖnh v c¸c gi¸ trÞ cña thËp vÞ ph©n. VÝ dô: . sum rlpcex1 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- rlpcex1 | 5999 3188.667 2692.567 357.318 45801.71 . sum rlpcex1, detail comp.M&Reg price adj.pc tot exp ------------------------------------------------------------- Percentiles Smallest 1% 682.9575 357.318 5% 1012.433 366.2792 10% 1238.088 376.9805 Obs 5999 25% 1671.054 381.3502 Sum of Wgt. 5999 50% 2397.042 Mean 3188.667 Largest Std. Dev. 2692.567 75% 3711.917 26944.64 90% 5940.803 30624.77 Variance 7249918 95% 8045.32 31066.5 Skewness 3.791027 99% 14163.04 45801.71 Kurtosis 29.21398
- 16. 16 3.8. HiÓn thÞth«ng tin chung vÒ biÕn Có ph¸p: inspect [danh s¸ch biÕn] [®iÒu kiÖn] [ph¹m vi] LÖnh n y m« t¶ vÒ sè liÖu cña c¸c biÕn kiÓu sè. Nã ®−a ra th«ng tin vÒ sè ©m, d−¬ng, sè nguyªn, gi¸ trÞ thiÕu (missing) cña gi¸ trÞ cña biÕn. VÝ dô: . gen x=invnorm(uniform()) . inspect x x: Number of Observations ---- Non- Total Integers Integers | # Negative 2964 - 2964 | # Zero - - - | # Positive 3035 - 3035 | # ----- ----- ----- | # # # Total 5999 - 5999 | . # # # . Missing - +---------------------- ----- -3.918931 3.641588 5999 (More than 99 unique values) Chó ý: cã thÓ xem thªm lÖnh codebook 3.9. T¹o b¶ng tÇn suÊt T¹o b¶ng tÇn suÊt 1 chiÒu Có ph¸p: tabulate <tªn biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, missing nolabel] tab1 <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, missing nolabel] LÖnh n y t¹o b¶ng tÇn suÊt 1 chiÒu cña biÕn ®−îc chØ ra. LÖnh tabulate chØ cho phÐp cã 1 biÕn ®−îc chØ ra, nÕu cã h¬n 1 biÕn ®−îc chØ ra th× Stata sÏ hiÓu l t¹o b¶ng tÇn suÊt 2 chiÒu. C¸c tuú chän: missing Cho phÐp c¸c quan s¸t kh«ng cã gi¸ trÞ (missing) ®−îc xÕp v o 1 lo¹i. nolabel Cho phÐp hiÓn thÞ gi¸ trÞ sè cña biÕn, chø kh«ng ph¶i nh n biÕn VÝ dô: . tab sex Gender of | HH.head | (1:M;2:F) | Freq. Percent Cum.
- 17. 17 ------------+----------------------------------- 1 | 437572.93 72.93 2 | 1624 27.07 100.00 ------------+----------------------------------- Total | 5999 100.00 . tab1 urban98 reg7 -> tabulation of urban98 1:urban 98; | 0:rural 98 | Freq. Percent Cum. ------------+----------------------------------- Rural | 4269 71.16 71.16 Urban | 1730 28.84 100.00 ------------+----------------------------------- Total | 5999 100.00 -> tabulation of reg7 Code by 7 | regions | Freq. Percent Cum. ------------+----------------------------------- region1 | 859 14.32 14.32 region2 | 1175 19.59 33.91 region3 | 708 11.80 45.71 region4 | 754 12.57 58.28 region5 | 368 6.13 64.41 region6 | 1023 17.05 81.46 region7 | 1112 18.54 100.00 ------------+----------------------------------- Total | 5999 100.00 Chóng ta còng cã thÓ dïng cöa sæ lÖnh b»ng menu bar
- 18. 18 T¹o b¶ng tÇnsuÊt 2 chiÒu Có ph¸p: tabulate <tªn biÕn 1> <tªn biÕn 2> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, chi2 missing nofreq cell column row] tab2 <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, chi2 missing nofreq cell column row] LÖnh tablulate n y tÝnh v hiÓn thÞ b¶ng tÇn suÊt 2 chiÒu cña 2 biÕn ®−îc chØ ra. LÖnh tab2 t¹o b¶ng tÇn suÊt 2 chiÒu cña tõng cÆp biÕn ®−îc chØ ra trong danh s¸ch biÕn. VÝ dô: . tab urban98 farm 1:urban | Type of HH (1:farm; 98; | 0:nonfarm) 0:rural 98 | non farm farm | Total -----------+----------------------+---------- Rural | 1021 3248 | 4269 Urban | 1540 190 | 1730 -----------+----------------------+---------- Total | 2561 3438 | 5999 C¸c tuú chän: chi2 Thùc hiÖn kiÓm ®Þnh gi¶ thiÕt l hai biÕn ®éc lËp
- 19. 19 missing Cho phÐpc¸c quan s¸t kh«ng cã gi¸ trÞ ®−îc xÕp v o 1 lo¹i nofreq Kh«ng hiÓn thÞ tÇn suÊt cell HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c « column HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c « theo cét row HiÓn thÞ tÇn suÊt t−¬ng ®èi (tû lÖ %) cña c¸c « theo h ng VÝ dô: . tab reg7 urban98, cell nof | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 11.20 3.12 | 14.32 region2 | 13.05 6.53 | 19.59 region3 | 10.00 1.80 | 11.80 region4 | 8.37 4.20 | 12.57 region5 | 6.13 0.00 | 6.13 region6 | 8.57 8.48 | 17.05 region7 | 13.84 4.70 | 18.54 -----------+----------------------+---------- Total | 71.16 28.84 | 100.00 . tab farm urban98, column row Type of HH | 1:urban 98; 0:rural (1:farm; | 98 0:nonfarm) | Rural Urban | Total -----------+----------------------+---------- non farm | 1021 1540 | 2561 | 39.87 60.13 | 100.00 | 23.92 89.02 | 42.69 -----------+----------------------+---------- farm | 3248 190 | 3438 | 94.47 5.53 | 100.00 | 76.08 10.98 | 57.31 -----------+----------------------+---------- Total | 4269 1730 | 5999 | 71.16 28.84 | 100.00 | 100.00 100.00 | 100.00 3.10. T¹o b¶ng thèng kª tæng hîp b»ng lÖnh tabulate…summarize Có ph¸p: tabulate <tªn biÕn 1> <tªn biÕn 2> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] , summarize(tªn biÕn 3) [means standard freq missing ] LÖnh n y t¹o b¶ng mét hoÆc hai chiÒu ®Þnh nghÜa bëi biÕn 1 hoÆc biÕn 2 v mçi « cho gi¸ trÞ thèng kª trung b×nh, ®é lÖch chuÈn v tÇn suÊt cña biÕn 3. VÝ dô:
- 20. 20 . tab farmurban98, sum(poor) Means, Standard Deviations and Frequencies of poor Type of HH | 1:urban 98; 0:rural (1:farm; | 98 0:nonfarm) | Rural Urban | Total -----------+----------------------+---------- non farm | .2791381 .06168831 | .14837954 | .44879538 .24066673 | .35554523 | 1021 1540 | 2561 -----------+----------------------+---------- farm | .42302956 .12105263 | .4063409 | .4941161 .32705022 | .49122109 | 3248 190 | 3438 -----------+----------------------+---------- Total | .3886156 .06820809 | .29621604 | .48749275 .25217555 | .45662551 | 4269 1730 | 5999 C¸c tuú chän: means HiÓn thÞ mçi gi¸ trÞ trung b×nh standard HiÓn thÞ mçi gi¸ trÞ ®é lÖch chuÈn freq HiÓn thÞ mçi gi¸ trÞ tÇn suÊt missing Cho phÐp c¸c quan s¸t kh«ng cã gi¸ trÞ ®−îc xÕp v o 1 lo¹i VÝ dô: . replace poor=poor*100 (1777 real changes made) . format poor %4.2f . tab reg7 urban98, sum(poor) means Means of poor | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 61.46 8.02 | 49.83 region2 | 32.57 5.87 | 23.66 region3 | 44.83 10.19 | 39.55 region4 | 37.25 11.51 | 28.65 region5 | 47.28 . | 47.28 region6 | 12.45 2.16 | 7.33 region7 | 35.78 10.28 | 29.32 -----------+----------------------+---------- Total | 38.86 6.82 | 29.62 3.11. T¹o b¶ng thèng kª tæng hîp b»ng lÖnh tabstat Có ph¸p:
- 21. 21 tabstat <danh s¸chbiÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, statistics(có ph¸p tkª [...]) by(tªn biÕn) missing format[(%fmt)]] LÖnh n y tÝnh to¸n c¸c thèng kª cña c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn cho tõng gi¸ trÞ cña biÕn ph©n lo¹i (categorical) ®−îc chØ ra bëi by(tªn biÕn). Chóng ta còng cã thÓ dïng cöa sæ lÖnh b»ng menu bar VÝ dô: . tabstat rlfood rlhhex1, stats(mean median) by(reg7) Summary statistics: mean, p50 by categories of: reg7 (Code by 7 regions) reg7 | rlfood rlhhex1 --------+-------------------- region1 | 5595.556 9560.349 | 5350.916 8536.373 ----------------------------- region2 | 6419.427 12951.14 | 5664.145 9997.146 ----------------------------- region3 | 5692.201 10885.38 | 5369.411 9022.334 ----------------------------- region4 | 6512.576 13525.41
- 22. 22 | 5790.046 11077.51 ----------------------------- region5| 5894.983 11217.05 | 5380.505 9421.447 ----------------------------- region6 | 9746.158 23515.01 | 8428.743 18514.39 ----------------------------- region7 | 6556.616 13068.11 | 6066.128 11043.99 ----------------------------- Total | 6787.898 14010.74 | 5951.567 10733.19 ----------------------------- C¸c tuú chän: statistics(statname [...]) ChØ ra thèng kª cÇn tÝnh cho danh s¸ch biÕn by(tªn biÕn) ChØ ra biÕn ph©n lo¹i (categorical) Missing Gi¸ trÞ thiÕu (mising) cña biÕn lo¹i ®−îc xem nh− 1 lo¹i format[(%fmt)] ChØ ra ®Þnh d¹ng cña sè liÖu hiÓn thÞ Stata cho phÐp c¸c lo¹i thèng kª ®−îc chØ ra bëi statistics(có ph¸p thèng kª [...]) nh− sau: Có ph¸p thèng kª ý nghÜa mean Trung b×nh mean count §Õm sè quan s¸t n Gièng nh− lÖnh count (§Õm sè quan s¸t) sum Tæng céng max Gi¸ trÞ lín nhÊt min Gi¸ trÞ nhá nhÊt range Biªn ®é = Gi¸ trÞ lín nhÊt - Gi¸ trÞ nhá nhÊt sd §é lÖch chuÈn sdmean §é lÖch chuÈn cña trung b×nh = §é lÖch chuÈn / {(Sè quan s¸t)^0.5} skewness §é lÖch cña ph©n phèi kurtosis §é nhän median Trung vÞ (Gièng nh− p50) p1 1% ph©n vÞ p5 5% ph©n vÞ p10 10% ph©n vÞ p25 25% ph©n vÞ p50 50% ph©n vÞ (trung vÞ)
- 23. 23 p75 75% ph©nvÞ p90 90% ph©n vÞ p95 95% ph©n vÞ p99 99% ph©n vÞ iqr p75 - p25 q t−¬ng ®−¬ng víi "p25 p50 p75" VÝ dô: . tabstat rlpcex1, stats(mean sd q) by(reg7) format(%5.1f) Summary for variables: rlpcex1 by categories of: reg7 (Code by 7 regions) reg7 | mean sd p25 p50 p75 --------+-------------------------------------------------- region1 | 2174.8 1265.1 1328.0 1792.1 2710.8 region2 | 3294.0 2511.9 1816.7 2532.5 3822.0 region3 | 2503.3 1918.0 1489.7 2001.2 2808.1 region4 | 2933.7 2260.5 1697.9 2362.2 3471.4 region5 | 2087.3 1285.4 1217.3 1850.8 2700.5 region6 | 5257.5 4005.7 2676.7 4154.1 6431.8 region7 | 2931.1 2137.2 1680.1 2321.9 3414.7 ----------------------------------------------------------- Total | 3188.7 2692.6 1671.1 2397.0 3711.9 ----------------------------------------------------------- 3.12. T¹o b¶ng thèng kª tæng hîp b»ng lÖnh table Có ph¸p: table <biÕn dßng> [biÕn cét [biÕn cét trªn cïng]] [®iÒu kiÖn] [ph¹m vi] [quyÒn sè] [, contents(néi dung) row col format(%fmt) missing] LÖnh n y cho phÐp tÝnh c¸c thèng kª cña c¸c biÕn ®−îc chØ ra trong contents theo d¹ng b¶ng, trong ®ã c¸c h ng ®−îc ®Þnh nghÜa bëi biÕn dßng, cßn c¸c cét ®−îc ®Þnh nghÜa bëi biÕn cét (v biÕn cét trªn cïng). C¸c biÕn h ng v cét n y l c¸c biÕn ph©n lo¹i (categorical). VÝ dô: . table reg7 urban98 farm, contents(mean poor) ---------------------------------------------------- | Type of HH (1:farm; 0:nonfarm) and | 1:urban 98; 0:rural 98 Code by 7 | ---- non farm ---- ------ farm ------ regions | Rural Urban Rural Urban ----------+----------------------------------------- region1 | 19.35484 6.015038 65.7377 12.96296 region2 | 26.66667 4.624278 33.96524 15.21739
- 24. 24 region3 | 40.9836110.11236 45.8159 10.52632 region4 | 21.6 11.63793 42.44032 10 region5 | 30.76923 49.24012 region6 | 15.04065 2.195609 10.07463 0 region7 | 38.62816 10.04184 34.35805 11.62791 ---------------------------------------------------- C¸c tuú chän: Contents(néi dung) LiÖt kª danh s¸ch c¸c biÕn v c¸c thèng kª. C¸c ký hiÖu thèng kª t−¬ng tù nh− ë lÖnh tabstat row HiÓn thÞ thèng kª tæng cña c¸c dßng col HiÓn thÞ thèng kª tæng cña c¸c cét format(%fmt) ChØ ra ®Þnh d¹ng cña sè liÖu hiÓn thÞ missing Gi¸ trÞ thiÕu (mising) cña biÕn lo¹i ®−îc xem nh− 1 lo¹i VÝ dô: . table reg7 urban98 farm, contents(mean poor) row col format(%4.2f) ------------------------------------------------------ | Type of HH (1:farm; 0:nonfarm) and 1:urban | 98; 0:rural 98 Code by 7 | ----- non farm ---- ------- farm ------ regions | Rural Urban Total Rural Urban Total ----------+------------------------------------------- region1 | 19.35 6.02 10.26 65.74 12.96 61.45 region2 | 26.67 4.62 11.29 33.97 15.22 32.70 region3 | 40.98 10.11 27.96 45.82 10.53 44.47 region4 | 21.60 11.64 15.13 42.44 10.00 40.81 region5 | 30.77 30.77 49.24 49.24 region6 | 15.04 2.20 6.43 10.07 0.00 9.78 region7 | 38.63 10.04 25.39 34.36 11.63 32.72 | Total | 27.91 6.17 14.84 42.30 12.11 40.63 ------------------------------------------------------ . table urban98 farm, contents(mean poor sd poor) row col format(%4.2f) ---------------------------------------- 1:urban | 98; | Type of HH (1:farm; 0:rural | 0:nonfarm) 98 | non farm farm Total ----------+----------------------------- Rural | 27.91 42.30 38.86 | 44.88 49.41 48.75 | Urban | 6.17 12.11 6.82 | 24.07 32.71 25.22 | Total | 14.84 40.63 29.62 | 35.55 49.12 45.66
- 25. 25 ---------------------------------------- . table urban98farm, contents(mean rlpcex1 mean rlhhex1) row col format(%4.2f) ---------------------------------------- 1:urban | 98; | Type of HH (1:farm; 0:rural | 0:nonfarm) 98 | non farm farm Total ----------+----------------------------- Rural | 2835.83 2212.12 2361.29 | 13242.03 10120.89 10867.36 | Urban | 5476.86 3232.17 5230.33 | 22984.44 11903.19 21767.43 | Total | 4423.95 2268.49 3188.67 | 19100.41 10219.39 14010.74 ---------------------------------------- 4. Biªn tËp v söa ch÷a d÷ liÖu (Data manipulation) 4.1.T¹o biÕn míi T¹o biÕn b»ng lÖnh generate Có ph¸p: generate <biÕn míi> = biÓu thøc [®iÒu kiÖn] [ph¹m vi] LÖnh n y cho phÐp t¹o biÕn míi cã gi¸ trÞ b»ng gi¸ trÞ cña biÓu thøc ®−îc chØ ra. VÝ dô: . gen poor = 1 if rlpcex1 < 1790 (4222 missing values generated) . gen nonpoor=1 if rlpcex1 >= 1790 (1777 missing values generated) LÖnh t¹o biÕn gi¶ tabulate…generate Có ph¸p: tabulate <biÕn ph©n lo¹i>, generate(biÕn míi) LÖnh generate cã thÓ kÕt hîp víi tab ®Ó t¹o c¸c biÕn gi¶ . BiÕn míi t¹o ra sÏ cã d¹ng l “biÕn míi 1”, “biÕn míi 2”, “biÕn míi 3”, v..v. BiÕn n y chÝnh l c¸c biÕn gi¶ ®−îc t¹o ra trªn c¬ së cña biÕn ph©n lo¹i. VÝ dô: . tab reg7, gen(region) Code by 7 |
- 26. 26 regions | Freq.Percent Cum. ------------+----------------------------------- region1 | 859 14.32 14.32 region2 | 1175 19.59 33.91 region3 | 708 11.80 45.71 region4 | 754 12.57 58.28 region5 | 368 6.13 64.41 region6 | 1023 17.05 81.46 region7 | 1112 18.54 100.00 ------------+----------------------------------- Total | 5999 100.00 . tab1 region1 region2 -> tabulation of region1 reg7==regio | n1 | Freq. Percent Cum. ------------+----------------------------------- 0 | 5140 85.68 85.68 1 | 859 14.32 100.00 ------------+----------------------------------- Total | 5999 100.00 -> tabulation of region2 reg7==regio | n2 | Freq. Percent Cum. ------------+----------------------------------- 0 | 4824 80.41 80.41 1 | 1175 19.59 100.00 ------------+----------------------------------- Total | 5999 100.00 ë ®©y biÕn reg7 cã 7 gi¸ trÞ tõ 1 ®Õn 7 t−¬ng øng víi 7 biÕn gi¶ tõ region1 ®Õn region7 sÏ ®−îc t¹o ra. BiÕn region1 nhËn gi¸ trÞ b»ng 1 nÕu nh− biÕn reg7 nhËn gi¸ trÞ 1, nÕu kh«ng th× b»ng 0. T−¬ng tù biÕn region7 nhËn gi¸ trÞ 1 nÕu nh− biÕn reg7 b»ng 7. ë vÝ dô trªn lÖnh tabulate…generate t−¬ng ®−¬ng víi 7 lÖnh sau: gen region1=(reg7==1) gen region2=(reg7==2) … gen region7=(reg7==7) T¹o biÕn b»ng lÖnh egen Có ph¸p: egen <biÕn míi> = fcn(tham sè) [®iÒu kiÖn] [ph¹m vi] [, by(biÕn)] LÖnh n y cho phÐp t¹o biÕn míi theo gi¸ trÞ cña h m sè ®−îc chØ ra bëi fcn. BiÕn míi n y sÏ nhËn gi¸ trÞ cè ®Þnh cho mäi quan s¸t. H m sè ë ®©y cã thÓ l : count(exp) §Õm sè quan s¸t cña biÓu thøc
- 27. 27 mean(exp) Cho gi¸trÞ trung b×nh cña biÓu thøc median(exp) Cho gi¸ trÞ trung vÞ cña biÓu thøc sd(exp) Cho gi¸ trÞ ®é lÖch chuÈn cña biÓu thøc C¸c h m sè kh¸c cã thÓ xem ë phÇn help egen. VÝ dô: . egen sumexp=sum(rlpcex1) . sum sumexp Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- sumexp | 5999 1.91e+07 0 1.91e+07 1.91e+07 . egen g=median( food+ nonfood1) . sum g Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- g | 5999 11063.6 0 11063.6 11063.6 Thay thÕ gi¸ trÞ cña biÕn Có ph¸p: replace <biÕn> = biÓu thøc [®iÒu kiÖn] [ph¹m vi] LÖnh n y thay thÕ gi¸ trÞ cña biÕn hiÖn cã b»ng gi¸ trÞ míi x¸c ®Þnh bëi biÓu thøc exp. VÝ dô: replace poor=poor*100 replace pcexp = hhexp/hhsize T¹o biÕn ph©n lo¹i b»ng lÖnh encode Có ph¸p: encode <biÕn> [®iÒu kiÖn] [ph¹m vi], generate(biÕn míi) LÖnh n y cho phÐp t¹o biÕn ph©n lo¹i míi (categorical) kiÓu sè t−¬ng øng víi c¸c gi¸ trÞ cña biÕn kiÓu ch÷ chØ ra bëi tªn biÕn (®−îc xÕp theo vÇn ch÷ c¸i). VÝ dô: . gen str15(mucsong) = "Kha" . drop mucsong . gen mucsong="Rat ngheo" type mismatch r(109);
- 28. 28 . gen str15(mucsong)="Ratngheo" . replace mucsong="Ngheo" if rlpcex1<1790 & rlpcex1>1290 (1087 real changes made) . replace mucsong="Khong ngheo" if rlpcex1>=1790 (4222 real changes made) . tab mucsong mucsong | Freq. Percent Cum. ----------------+----------------------------------- Khong ngheo | 4222 70.38 70.38 Ngheo | 1087 18.12 88.50 Rat ngheo | 690 11.50 100.00 ----------------+----------------------------------- Total | 5999 100.00 . sum mucsong Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- mucsong | 0 . encode mucsong, gen(ma_ms) . tab ma_ms ma_ms | Freq. Percent Cum. ------------+----------------------------------- Khong ngheo | 4222 70.38 70.38 Ngheo | 1087 18.12 88.50 Rat ngheo | 690 11.50 100.00 ------------+----------------------------------- Total | 5999 100.00 . sum ma_ms Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- ma_ms | 5999 1.411235 .6871957 1 3 T¹o biÕn b»ng lÖnh xtile Có ph¸p: xtile <biÕn míi> = biÓu thøc [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, nquantiles(#)] LÖnh n y t¹o biÕn ph©n nhãm cho biÓu thøc theo ph©n vÞ. Trong ®ã nquantiles(#) chØ ra sè l−îng ph©n vÞ. VÝ dô: T¹o biÕn ngò vÞ ph©n theo chi tiªu . xtile quinexp= rlpcex1, nq(5) . tab quinexp
- 29. 29 5 quantiles | ofrlpcex1 | Freq. Percent Cum. ------------+----------------------------------- 1 | 1200 20.00 20.00 2 | 1200 20.00 40.01 3 | 1200 20.00 60.01 4 | 1200 20.00 80.01 5 | 1199 19.99 100.00 ------------+----------------------------------- Total | 5999 100.00 . tab quinexp, sum( rlpcex1) | Summary of comp.M&Reg price adj.pc 5 quantiles | tot exp of rlpcex1 | Mean Std. Dev. Freq. ------------+------------------------------------ 1 | 1184.3975 261.20537 1200 2 | 1803.6331 151.66604 1200 3 | 2408.4867 211.5407 1200 4 | 3390.1065 403.08913 1200 5 | 7160.021 3690.3672 1199 ------------+------------------------------------ Total | 3188.6671 2692.5673 5999 4.2.§æi tªn biÕn Có ph¸p: rename <tªn biÕn có> <tªn biÕn míi> LÖnh n y thùc hiÖn viÖc ®æi tªn cò cña mét biÕn sang tªn míi. VÝ dô: rename poor nguoingheo rename rpcexp1 chitieu 4.3. LÖnh xo¸ biÕn, xo¸ quan s¸t Có ph¸p: drop <danh s¸ch biÕn> LÖnh n y xo¸ biÕn ®−îc chØ ra bëi danh s¸ch biÕn drop <®iÒu kiÖn> LÖnh n y xo¸ quan s¸t tho¶ m n ®iÒu kiÖn biÓu thøc drop <ph¹m vi> [®iÒu kiÖn] LÖnh n y xo¸ quan s¸t ®−îc chØ ra bëi ph¹m vi (v cã thÓ ph¶i tho¶ m n ®iÒu kiÖn biÓu thøc) keep <danh s¸ch biÕn> LÖnh n y gi÷ l¹i c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn, c¸c biÕn kh«ng ®−îc chØ ra sÏ bÞ xo¸ ®i keep <®iÒu kiÖn> LÖnh n y gi÷ l¹i c¸c quan s¸t tho¶ m n ®iÒu kiÖn biÓu thøc, c¸c quan s¸t kh¸c sÏ bÞ xo¸ ®i keep <ph¹m vi> [®iÒu kiÖn] LÖnh n y gi÷ l¹i c¸c quan s¸t ®−îc chØ ra bëi ph¹m vi (v cã thÓ tho¶ m n ®iÒu kiÖn biÓu thøc), c¸c quan s¸t kh¸c sÏ bÞ xo¸ ®i.
- 30. 30 VÝ dô: drop poorurban98 Xo¸ 2 biÕn poor v urban98 drop if sex==1 Xo¸ c¸c quan s¸t cã biÕn sex nhËn gi¸ trÞ b»ng 1 drop in 1/20 Xo¸ quan s¸t tõ 1 ®Õn 20 keep househol ChØ gi÷ l¹i biÕn househol, c¸c biÕn kh¸c bÞ xo¸ ®i keep in f/50 Gi÷ l¹i quan s¸t tõ ®Çu tiªn ®Õn 50, c¸c quan s¸t kh¸c bÞ xo¸ ®i 4.4. LÖnh ®æi gi¸ trÞ cña biÕn ph©n lo¹i Có ph¸p: recode <tªn biÕn> gi¸ trÞ cò = gi¸ trÞ míi [®iÒu kiÖn] [ph¹m vi] LÖnh n y ®æi gi¸ trÞ cña biÕn ph©n lo¹i theo c¸c quy t¾c ®−îc chØ ra ë sau ®ã. VÝ dô: . recode sex 0=1 (0 changes made) . recode sex . = 0 (0 changes made) . recode hhsize 1/5=1 6/10 = 2 * = 3 (5785 changes made) . tab hhsize Household | size | Freq. Percent Cum. ------------+----------------------------------- 1 | 4164 69.41 69.41 2 | 1786 29.77 99.18 3 | 49 0.82 100.00 ------------+----------------------------------- Total | 5999 100.00 . tab urban98 1:urban 98; | 0:rural 98 | Freq. Percent Cum. ------------+----------------------------------- Rural | 4269 71.16 71.16 Urban | 1730 28.84 100.00 ------------+----------------------------------- Total | 5999 100.00 . recode urban98 0=1 1=0 (5999 changes made) . tab urban98 1:urban 98; |
- 31. 31 0:rural 98 |Freq. Percent Cum. ------------+----------------------------------- Rural | 1730 28.84 28.84 Urban | 4269 71.16 100.00 ------------+----------------------------------- Total | 5999 100.00 4.5. LÖnh g¸n nh·n cho biÕn G¸n nh·n cho biÕn Có ph¸p: label variable <tªn biÕn> “Nh·n cña biÕn” LÖnh n y g¸n nh n l mét dÉy ký tù cho biÕn. VÝ dô: . gen ngheo=poor . des ngheo storage display value variable name type format label variable label --------------------------------------------------------------------------- ngheo float %9.0g . tab ngheo ngheo | Freq. Percent Cum. ------------+----------------------------------- 0 | 4222 70.38 70.38 1 | 1777 29.62 100.00 ------------+----------------------------------- Total | 5999 100.00 . label var ngheo "Nguoi co thu nhap duoi chuan ngheo" . tab ngheo Nguoi co | thu nhap | duoi chuan | ngheo | Freq. Percent Cum. ------------+----------------------------------- 0 | 4222 70.38 70.38 1 | 1777 29.62 100.00 ------------+----------------------------------- Total | 5999 100.00 . des ngheo storage display value variable name type format label variable label ---------------------------------------------------------------------------- ngheo float %9.0g Nguoi co thu nhap duoi chuan ngheo G¸n gi¸ trÞ cho biÕn ph©n lo¹i label define <tªn bé nh·n> # "nh·n" [# "nh·n" ...] [, add modify]
- 32. 32 label dir label list<tªn bé nh·n> label drop {tªn bé nh·n [tªn bé nh·n ...] | _all} label values <tªn biÕn> [tªn bé nh·n] LÖnh label define g¸n nh n cho mét bé gi¸ trÞ sè. Tªn cña bé nh n ®−îc chØ ra sau tõ kho¸ define, # l gi¸ trÞ sè, “nh·n” l chuçi ký tù t−¬ng øng víi gi¸ trÞ sè ®Êy. Cã hai tuú chän ë ®©y: tuú chän add thªm gi¸ trÞ v nh n t−¬ng øng v o 1 bé nh n ® cã s½n. Tuú chän modify cho phÐp söa ch÷a gi¸ trÞ v nh n cña 1 bé nh n ® cã s½n. LÖnh label dir hiÓn thÞ nh÷ng bé nh n cã s½n, cßn lÖnh label list hiÓn thÞ gi¸ trÞ cña bé nh n ®−îc chØ ra. LÖnh label drop xo¸ c¸c bé nh n cã s½n. VÝ dô: T¹o nh n cã tªn l nngheo víi gi¸ trÞ 1 cã nghÜa l ng−êi nghÌo, cßn 0 cã nghÜa l ng−êi kh«ng nghÌo. . label define nngheo 0 "Ngheo" 1 "Khong ngheo" . label dir nngheo region loaiho diploma urban agegroup . label list nngheo nngheo: 0 Khong ngheo 1 Ngheo . label drop _all . label dir LÖnh label values sÏ g¸n c¸c nh n cña 1 bé nh n cho c¸c gi¸ trÞ sè cña 1 biÕn ph©n lo¹i. VÝ dô: . tab ngheo ngheo | Freq. Percent Cum. ------------+----------------------------------- 0 | 4222 70.38 70.38 1 | 1777 29.62 100.00 ------------+----------------------------------- Total | 5999 100.00 . list ngheo in 1/5 ngheo 1. 1
- 33. 33 2. 0 3. 1 4.1 5. 0 . label values ngheo nngheo . tab ngheo ngheo | Freq. Percent Cum. ------------+----------------------------------- Ngheo | 4222 70.38 70.38 Khong ngheo | 1777 29.62 100.00 ------------+----------------------------------- Total | 5999 100.00 . list ngheo in 1/5 ngheo 1. Khong ngheo 2. Ngheo 3. Khong ngheo 4. Khong ngheo 5. Ngheo 4.6. S¾p xÕp sè liÖu Có ph¸p: sort <danh s¸ch biÕn> [ph¹m vi] gsort [+|-]tªn biÕn [[+|-]tªn biÕn [...]] LÖnh sort s½p xÕp quan s¸t theo thø tù t¨ng dÇn cña gi¸ trÞ cña c¸c biÕn ®−îc chØ ra trong danh s¸ch biÕn. LÖnh gsort cho phÐp s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña cña c¸c biÕn (danh s¸ch biÕn), nÕu dÊu + ®−îc chØ ra (®©y còng l gi¸ trÞ ngÇm ®Þnh), hoÆc theo thø tù gi¶m dÇn, nÕu dÊu - ®−îc chØ ra. VÝ dô: sort reg7 hhsize LÖnh n y s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña biÕn vïng reg7, trong mçi vïng c¸c quan s¸t l¹i ®−îc s½p xÕp theo thø tù t¨ng dÇn cña biÕn quy m« hé hhsize. gsort reg7 –hhsize LÖnh n y s½p xÕp c¸c quan s¸t theo thø tù t¨ng dÇn cña biÕn vïng reg7, nh−ng trong mçi vïng c¸c quan s¸t l¹i ®−îc s½p xÕp theo thø tù gi¶m dÇn cña biÕn quy m« hé hhsize. 4.7. Trén sè liÖu LÖnh thu gän sè liÖu - collapse Có ph¸p: collapse <biÓu thøc thèng kª> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, by(danh s¸ch biÕn)]
- 34. 34 trong ®ã: BiÓu thøcthèng kª l danh s¸ch c¸c thèng kª v c¸c biÕn t−¬ng øng. C¸c thèng kª ®−îc ký hiÖu nh− môc 3.12 cña ch−¬ng n y. LÖnh collapse sÏ t¹o ra mét tÖp sè liÖu míi bao gåm c¸c biÕn ®−îc chØ ra bëi danh s¸ch biÕn, víi c¸c gi¸ trÞ ®−îc tÝnh theo thèng kª t−¬ng øng. C¸c quan s¸t cña tÖp sè liÖu cò sÏ ®−îc nhãm l¹i theo c¸c gi¸ trÞ cïng lo¹i cña biÕn ®−îc chØ ra bëi by(danh s¸ch biÕn). VÝ dô: Chóng ta cã file sè liÖu vÒ thu nhËp v chi tiªu cña c¸c hé th nh viªn trong gia ®×nh: ma_tv ma_ho thunhap Chitieu 1 101 200 500 2 101 1200 400 3 101 0 200 4 101 0 200 1 102 3200 500 2 102 1200 320 3 102 200 200 1 103 300 500 2 103 2100 250 3 103 0 300 4 103 0 300 1 104 4300 800 2 104 3500 500 3 104 300 500 4 104 0 300 5 104 0 200 6 104 0 200 Chóng ta sÏ dïng lÖnh collapse ®Ó t¹o file vÒ thu nhËp v chi tiªu b×nh qu©n cña c¸c hé, v t¹o thªm 1 biÕn vÒ qui m« hé. . gen quimo=1 . collapse (mean) thunhap (mean) chitieu (sum) quimo, by(ma_ho) TÖp sè liÖu míi cã d¹ng: ma_ho thunhap chitieu quimo 101 350 325 4 102 1533.33 340 3 103 600 337.5 4 104 1350 416.667 6 KÕt hîp sè liÖu - lÖnh merge Có ph¸p: merge [danh s¸ch biÕn] using <tªn tÖp sö dông> [, update replace]
- 35. 35 LÖnh merge sÏnèi c¸c quan s¸t cña tÖp sè liÖu ®ang më trong Stata (gäi l tÖp chñ (master dataset)) víi c¸c quan s¸t t−¬ng øng cña tÖp sè liÖu kh¸c ®−îc chØ ra sau tõ kho¸ using (gäi l tÖp sö dông (using dataset)) th nh 1 tÖp míi. C¸c biÕn chØ ra trong danh s¸ch biÕn ®−îc gäi l biÕn x¸c ®Þnh (identifying variables), v ph¶i ®−îc s½p xÕt b»ng lÖnh sort (hoÆc gsort) tr−íc khi thùc hiÖn lÖnh merge. VÝ dô: Chóng ta cã 2 tÖp sè liÖu nh− sau: thunhap.dta ma_ho thunhap chitieu quimo 101 350 325 4 102 1533.33 340 3 103 600 337.5 4 104 1350 416.667 6 dialy.dta ma_ho thanhthi vung 204 0 1 102 1 4 103 0 3 104 0 6 LÖnh merge sÏ ®−îc thùc hiÖn nh− sau: . use "C:dialy.dta", clear . sort ma_ho . save "C:dialy.dta" file C:dialy.dta saved . use "C:thunhap.dta", clear . sort ma_ho . merge ma_ho using "C:dialy.dta" ma_ho was byte now int . edit TÖp kÕt qu¶ cã d¹ng nh− sau: ma_ho thunhap chitieu quimo thanhthi vung _merge 101 350 325 4 . . 1 102 1533.33 340 3 1 4 3 103 600 337.5 4 0 3 3 104 1350 416.667 6 0 6 3 204 . . . 0 1 2 Trong tÖp kÕt qu¶ cã thªm 1 biÕn tªn l _merge, biÕn n y nhËn c¸c gi¸ trÞ nh− sau: _merge==1 NÕu nh− quan s¸t chØ ®−îc t¹o tõ tÖp chñ _merge==2 NÕu nh− quan s¸t chØ ®−îc t¹o tõ sö dông
- 36. 36 _merge==3 NÕu nh−quan s¸t ®−îc t¹o tõ c¶ tÖp chñ v tÖp sö dông C¸c tuú chän: Trong tr−êng hîp hai tÖp sè liÖu cã c¸c biÕn trïng nhau, c¸c tuú chän sau ®©y cho phÐp xö lý sè liÖu theo c¸c c¸ch kh¸c nhau: update NÕu sè liÖu cña biÕn trïng nhau cña tÖp chñ cã gi¸ trÞ thiÕu th× gi¸ trÞ thiÕu n y nhËn gi¸ trÞ cña biÕn trïng nhau cña tÖp sö dông. replace Gi¸ trÞ cña biÕn trïng nhau cña tÖp chñ sÏ nhËn gi¸ trÞ cña biÕn trïng nhau cña tÖp sö dông. NÕu kh«ng tuú chän n o ®−îc chØ ra th× theo ngÇm ®Þnh, gi¸ trÞ cña biÕn cña tÖp chñ sÏ kh«ng thay ®æi. Nèi sè liÖu – lÖnh append Có ph¸p: append using <tªn tÖp> LÖnh n y cho phÐp nèi tÖp ®−îc chØ ra bëi using v o víi tÖp ®ang ®−îc më theo c¸c biÕn cã cïng tªn v ®Þnh d¹ng. Sè quan s¸t cña tÖp míi b»ng tæng sè sè quan s¸t cña 2 tÖp. VÝ dô: cã tÖp thunhap2.dta nh− sau ma_ho thunhap chitieu gioitinh 105 1350 425 1 106 1500 370 0 107 800 556 0 108 1500 417 0 109 2500 540 1 Hai tÖp n y sÏ ®−îc nèi víi nhau b»ng lÖnh append nh− sau: . use "C:thunhap.dta", clear . append using "C:thunhap2.dta" . edit TÖp kÕt qu¶ cã d¹ng: ma_ho thunhap chitieu quimo gioitinh 101 350 325 4 102 1533.33 340 3 103 600 337.5 4 104 1350 416.667 6 105 1350 425 1 106 1500 370 0 107 800 556 0 108 1500 417 0 109 2500 540 1 Chó ý: Xem thªm lÖnh expand dung ®Ó t¹o ra c¸c quan s¸t gièng nhau. 4.8. ChuyÓn d¹ng sè liÖu
- 37. 37 Có ph¸p: reshape wide<tªn biÕn>, i(danh s¸ch biÕn) [ j(tªn biÕn [values]) ... ] reshape long <tªn biÕn>, i(danh s¸ch biÕn) [ j(tªn biÕn [values]) ... ] reshape wide reshape long LÖnh n y cho phÐp chuyÓn sè liÖu tõ d¹ng ngang sang sè liÖu d¹ng däc (tuú chän long), v tõ d¹ng däc sang d¹ng ngang (tuú chän wide). i(danh s¸ch biÕn) chØ ra biÕn x¸c ®Þnh (indentifying variables) dïng ®Ó ph©n biÖt c¸c quan s¸t víi nhau trong sè liÖu d¹ng ngang (gäi l quan s¸t cÊp 1). j(tªn biÕn) chØ ra biÕn dïng ®Ó ph©n biÖt gi÷a c¸c quan s¸t cÊp 2 ë sè liÖu d¹ng däc. VÝ dô 1: Chóng ta cã thÓ sè liÖu d¹ng b¶ng ngang nh− mét ma trËn nh− sau: - i - -------------------- xÞj ------------------- maho quimo thunhap95 thunhap96 thunhap97 101 5 4500 4400 5400 102 4 3400 3300 3700 103 6 5000 5400 5500 sè liÖu n y sÏ ®−îc chuyÓn sang d¹ng b¶ng däc nh− sau: - i - - j - - xji - maho quimo nam thunhap 101 5 95 4500 101 5 96 4400 101 5 97 5400 102 4 95 3400 102 4 96 3300 102 4 97 3700 103 6 95 5000 103 6 96 5400 103 6 97 5500 V lÖnh reshape sÏ ®−îc viÕt nh− sau: . reshape long thunhap, i(maho) j(nam) (note: j = 95 96 97) Data wide -> long --------------------------------------------------------------------- Number of obs. 3 -> 9 Number of variables 5 -> 4 j variable (3 values) -> nam xij variables: thunhap95 thunhap96 thunhap97 -> thunhap --------------------------------------------------------------------- * Va chuyen nguoc lai tu dang doc sang dang ngang nhu sau . reshape wide thunhap, i(maho) j(nam) (note: j = 95 96 97)
- 38. 38 Data long ->wide ------------------------------------------------------------------------ Number of obs. 9 -> 3 Number of variables 4 -> 5 j variable (3 values) nam -> (dropped) xij variables: thunhap -> thunhap95 thunhap96 thunhap97 ---------------------------------------------------------------------- VÝ dô 2: Chóng ta cã sè liÖu d¹ng b¶ng sau ®©y: maho sotien1 nguon1 sotien2 nguon2 101 1200 “Ngan hang A” 2000 “Ngan hang A” 102 1300 “Ngan hang B” . . 103 2500 “Ngan hang A” 1000 “Ngan hang C” 104 3000 “Ngan hang A” 2000 “Ngan hang B” B¶ng n y ®−îc chuyÓn sang b¶ng d¹ng däc nh− sau: . reshape long sotien nguon, i(maho) j(lanvay) (note: j = 1 2) Data wide -> long --------------------------------------------------------------------- Number of obs. 4 -> 8 Number of variables 5 -> 4 j variable (2 values) -> lanvay xij variables: sotien1 sotien2 -> sotien nguon1 nguon2 -> nguon --------------------------------------------------------------------- B¶ng däc cã d¹ng nh− sau: maho lanvay sotien nguon 101 1 1200 Ngan hang A 101 2 2000 Ngan hang A 102 1 1300 Ngan hang B 102 2 103 1 2500 Ngan hang A 103 2 1000 Ngan hang C 104 1 3000 Ngan hang A 104 2 2000 Ngan hang B 5. QuyÒn sè trong VHLSS (Weight) 5.1. QuyÒn sè trong ®iÒu tra chän mÉu Trong ®iÒu tra chän mÉu, c¸c quan s¸t ®−îc lùa chän mét c¸ch ngÉu nhiªn nh−ng th«ng th−êng c¸c quan s¸t th−êng cã x¸c suÊt lùa chän kh¸c nhau. QuyÒn sè b»ng gi¸ trÞ nghÞch ®¶o cña x¸c suÊt ®−îc chän v o mÉu. NÕu nh− quan s¸t i cã quyÒn sè l wi th× cã thÓ nãi quan s¸t i trong mÉu ®¹i diÖn cho wi
- 39. 39 phÇn tö trongtæng thÓ. C¸c −íc l−îng suy diÔn vÒ tæng thÓ cÇn ph¶i tÝnh ®Õn quyÒn sè chän mÉu, nÕu kh«ng th× kÕt qu¶ sÏ bÞ sai lÖch. VÝ dô: Gi¶ sö miÒn §ång b»ng S«ng Hång gåm 2 tØnh l H Néi v B¾c Ninh víi d©n sè t−¬ng øng l 4.5 triÖu v 500 ngh×n ng−êi. Chóng ta muèn chän mét mÉu ngÉu nhiªn víi cì mÉu l 500 quan s¸t ®Ó nghiªn cøu vÒ thu nhËp cña §ång b»ng S«ng Hång còng nh− 2 tØnh n y. NÕu nh− theo tû lÖ vÒ d©n sè gi÷a 2 tØnh th× chóng ta sÏ thu ®−îc mÉu gåm 450 hé t¹i H Néi v 50 hé t¹i Nam §Þnh. Tuy nhiªn mÉu ®−îc chän mét c¸ch ngÉu nhiªn trªn c¶ vïng nªn sÏ cã kh¶ n¨ng l chóng ta thu ®−îc mét mÉu m kh«ng cã quan s¸t n o cña tØnh Nam §Þnh, hoÆc cã víi sè l−îng rÊt nhá. §Ó cho mÉu mang tÝnh ®¹i diÖn cho c¸c tØnh th× nªn chän 400 quan s¸t t¹i H Néi v 100 quan s¸t t¹i Nam §Þnh. NÕu thu nhËp b×nh qu©n cña H Néi l 900 ngh×n/ th¸ng, v cña Nam §Þnh l 300 ngh×n/th¸ng th× thu nhËp b×nh qu©n cña c¶ vïng §ång b»ng S«ng Hång kh«ng thÓ tÝnh l (900 + 300)/2, v× c¸c quan s¸t trong mÉu kh«ng ®−îc chän tû lÖ víi c¸c tØnh. Mçi quan s¸t t¹i H néi ®¹i diÖn cho 11250 hé trong vïng (4500000/400). §©y chÝnh l quyÒn sè cña quan s¸t, b»ng gi¸ trÞ nghÞch ®¶o cña x¸c suÊt ®−îc chän v o mÉu. Cßn mçi quan s¸t t¹i Nam §Þnh ®¹i diÖn cho 50000 quan s¸t cña vïng (500000/100). Thu nhËp cña vïng §ång b»ng S«ng Hång sÏ ®−îc tÝnh nh− sau: 840 5000010011250400 5000010030011250400900 nhapThu = ×+× ××+×× = Trong VLSS 1998 cã 2 quyÒn sè. Thø nhÊt l quyÒn sè hé, biÕn wt, chÝnh l sè hé cña ViÖt Nam m mçi hé ®¹i diÖn. QuyÒn sè thø hai l quyÒn sè cña th nh viªn hé, hhsizewt l sè ng−êi ViÖt Nam m mçi th nh viªn cña hé ®¹i diÖn. QuyÒn sè cña th nh viªn hé b»ng quyÒn sè hé nh©n víi quy m« hé. VÝ dô: QuyÒn sè trong VLSS 1998 . tab reg7, sum(wt) Code by 7 | Summary of sample quyÒn sè regions | Mean Std. Dev. Freq. ------------+------------------------------------ region1 | 3218.4296 850.74246 859 region2 | 3133.7277 849.12325 1175 region3 | 3185.1794 801.74266 708 region4 | 2199.37 492.37202 754 region5 | 1336.3098 269.14747 368 region6 | 1963.8964 528.69328 1023 region7 | 2938.2122 547.72125 1112 ------------+------------------------------------ Total | 2688.5003 900.01379 5999 . tab reg7, sum(hhsizewt) Code by 7 | Summary of =hhsize*wt regions | Mean Std. Dev. Freq. ------------+------------------------------------ region1 | 15790.857 7555.7552 859 region2 | 12656.003 5970.9089 1175 region3 | 14814.504 7236.7592 708 region4 | 10794.537 5235.562 754 region5 | 7564.731 3185.9336 368
- 40. 40 region6 | 9447.70774535.0816 1023 region7 | 14653.702 6639.8297 1112 ------------+------------------------------------ Total | 12636.546 6597.6574 5999 . di 2688.5003*5999 16128313 . di 12636.546*5999 75806639 5.2. C¸c lùa chän vÒ quyÒn sè Stata cho phÐp sö dông 4 lo¹i lo¹i quyÒn sè sau ®©y: fweights: quyÒn sè tÇn suÊt (frequency weights), Stata sÏ hiÓu quyÒn sè ë ®©y cã nghÜa l sè lÇn m mçi quan s¸t mçi quan s¸t ®−îc lÆp l¹i trong tÝnh to¸n. pweights: quyÒn sè chän mÉu (sampling weights), Stata sÏ hiÓu quyÒn sè l gi¸ trÞ nghÞch ®¶o cña x¸c suÊt ®−îc chän v o mÉu, hay sè phÇn tö trong t«ng thÓ m mçi quan s¸t trong mÉu ®¹i diÖn. aweights quyÒn sè ph©n tÝch (analytical weights), Stata sÏ hiÓu quyÒn sè tû lÖ nghÞch víi ph−¬ng sai cña quan s¸t. iweights quyÒn sè quan träng (importance weights), ®©y l quyÒn sè chØ møc ®é quan träng cña c¸c quan s¸t. §èi víi §iÒu tra møc sèng c¸c lÖnh sö dông quyÒn sè pweights v fweights. VÝ dô: . sum poor Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- poor | 5999 29.6216 45.66255 0 100 . sum poor [fw=hhsize] Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- poor | 28509 34.17517 47.43051 0 100 . . . tab reg7 urban98 | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 672 187 | 859 region2 | 783 392 | 1175 region3 | 600 108 | 708 region4 | 502 252 | 754 region5 | 368 0 | 368
- 41. 41 region6 | 514509 | 1023 region7 | 830 282 | 1112 -----------+----------------------+---------- Total | 4269 1730 | 5999 . . tab reg7 urban98 [fw= hhsizewt] | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 11993763 1570583 | 13564346 region2 | 11057932 3812871 | 14870803 region3 | 9582621 906048 | 10488669 region4 | 5618709 2520372 | 8139081 region5 | 2783821 0 | 2783821 region6 | 4545303 5119702 | 9665005 region7 | 13220727 3074190 | 16294917 -----------+----------------------+---------- Total | 58802876 17003766 | 75806642 . tab reg7 urban98 , sum(hhsize) means Means of Household size | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 5.1205357 3.7326203 | 4.8183935 region2 | 4.045977 4.0459184 | 4.0459574 region3 | 4.6666667 4.6759259 | 4.6680791 region4 | 4.8027888 5.1190476 | 4.9084881 region5 | 5.7065217 . | 5.7065217 region6 | 5.0719844 4.7131631 | 4.8934506 region7 | 5.1373494 4.3971631 | 4.9496403 -----------+----------------------+---------- Total | 4.8702272 4.4612717 | 4.752292 . tab reg7 urban98 [fw=wt], sum(hhsize) means Means and Number of Observations of Household size | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban | Total -----------+----------------------+---------- region1 | 5.1328749 3.6698008 | 4.9063857 | 2336656 427975 | 2764631 -----------+----------------------+---------- region2 | 4.0564115 3.987975 | 4.0386415 | 2726038 956092 | 3682130 -----------+----------------------+----------
- 42. 42 region3 | 4.65089084.6530097 | 4.6510738 | 2060384 194723 | 2255107 -----------+----------------------+---------- region4 | 4.8136253 5.132367 | 4.9080132 | 1167251 491074 | 1658325 -----------+----------------------+---------- region5 | 5.6609112 . | 5.6609112 | 491762 0 | 491762 -----------+----------------------+---------- region6 | 5.0486426 4.6174858 | 4.8106956 | 900302 1108764 | 2009066 -----------+----------------------+---------- region7 | 5.1494132 4.3925283 | 4.9872852 | 2567424 699868 | 3267292 -----------+----------------------+---------- Total | 4.8003065 4.3841133 | 4.7002214 | 12249817 3878496 | 16128313 . . table reg7 urban98 , c(mean poor) col row format(%4.1f) ------------------------------- | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban Total ----------+-------------------- region1 | 61.5 8.0 49.8 region2 | 32.6 5.9 23.7 region3 | 44.8 10.2 39.5 region4 | 37.3 11.5 28.6 region5 | 47.3 47.3 region6 | 12.5 2.2 7.3 region7 | 35.8 10.3 29.3 | Total | 38.9 6.8 29.6 ------------------------------- . table reg7 urban98 [pw=hhsizewt], c(mean poor) col row format(%4.1f) ------------------------------- | 1:urban 98; 0:rural Code by 7 | 98 regions | Rural Urban Total ----------+-------------------- region1 | 65.2 8.3 58.6 region2 | 36.1 7.0 28.7 region3 | 51.3 14.3 48.1 region4 | 43.6 16.6 35.2 region5 | 52.4 52.4 region6 | 13.0 2.9 7.6 region7 | 42.0 15.3 36.9 | Total | 45.5 9.2 37.4 -------------------------------
- 43. 43 Ch−¬ng III: KiÓm®Þnh gi¶ thiÕt vµ ph©n tÝch håi quy 1. ¦íc l−îng v kiÓm ®Þnh gi¶ thiÕt (Estimation and hypothesis testing) 1.1. ¦íc l−îng gi¸ trÞ trung b×nh b»ng kho¶ng tin cËy Có ph¸p: ci [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, level(#) binomial poisson exposure(tªn biÕn) total] LÖnh n y tÝnh sai sè chuÈn v kho¶ng tin cËy cho gi¸ trÞ trung b×nh cña mÉu theo quy luËt chuÈn, nhÞ thøc v Poatx«ng. C¸c tuú chän: level(#) chØ ®Þnh møc ®é tin cËy cho −íc l−îng kho¶ng tin cËy. # nhËn gi¸ trÞ tõ 10 ®ªn 99, gi¸ trÞ ngÇm ®Þnh l 95. binomial ¸p dông cho quy luËt nhÞ thøc poisson ¸p dông cho quy luËt Poatx«ng exposure(tªn biÕn) ¸p dông cho quy luËt Poatx«ng, tªn biÕn chØ ra biÕn “thêi l−îng” (th«ng th−êng l thêi gian hoÆc diÖn tÝch) m trong ®ã x¶y ra c¸c “sù kiÖn” ®−îc chØ ra bëi danh s¸ch biÕn total dïng khi ma “by prefix” ®−îc sö dung, yªu cÇu −íc l−îng kho¶ng tin cËy cho to n bé nhãm. VÝ dô: . ci poor Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 5999 29.6216 .5895501 28.46587 30.77733 . . . sort reg7 . by reg7: ci poor, total _______________________________________________________________________________ -> reg7 = region1 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 859 49.82538 1.706961 46.47507 53.17569 _______________________________________________________________________________ -> reg7 = region2 Variable | Obs Mean Std. Err. [95% Conf. Interval]
- 44. 44 -------------+------------------------------------------------------------- poor | 117523.65957 1.240357 21.22601 26.09314 _______________________________________________________________________________ -> reg7 = region3 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 708 39.54802 1.838899 35.93767 43.15838 _______________________________________________________________________________ -> reg7 = region4 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 754 28.64721 1.64759 25.4128 31.88163 _______________________________________________________________________________ -> reg7 = region5 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 368 47.28261 2.606121 42.1578 52.40741 _______________________________________________________________________________ -> reg7 = region6 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 1023 7.331378 .8153306 5.731465 8.931292 _______________________________________________________________________________ -> reg7 = region7 Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 1112 29.31655 1.365709 26.63689 31.99621 _______________________________________________________________________________ -> Total Variable | Obs Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- poor | 5999 29.6216 .5895501 28.46587 30.77733 Chó ý: C¸c lÖnh −íc l−îng cã thÓ ®−îc sö dông khi biÕt c¸c tham sè vÒ mÉu. §©y cã thÓ ®−îc gäi l “c¸c lÖnh sö dông tham sè trùc tiÕp” (Commands using immediate arguments). C¸c lÖnh n y rÊt h÷u dông khi chóng ta kh«ng cã sè liÖu gèc vÒ biÕn. cii <sè quan s¸t> <gi¸ trÞ trungb×nh> <®é lÖch chuÈn> [, level(#) ] (ph©n phèi chuÈn) cii <sè quan s¸t> <sè lÇn th nh c«ng cña quan s¸t> [, level(#) ] (ph©n phèi nhÞ thøc)
- 45. 45 #obs chØ rasè quan s¸t, #succ chØ ra sè lÇn gi¸ trÞ biÕn nhËn gi¸ trÞ t−¬ng øng víi phÐp thö th nh c«ng (th«ng th−êng nhËn gi¸ trÞ b»ng 1) cii <gi¸ trÞ thêi l−îng> <sè lÇn sù kiÖn x¶y ra> poisson [ level(#) ] (ph©n phèi Poatx«ng) VÝ dô: . cii 5999 1777, level (90) -- Binomial Exact -- Variable | Obs Mean Std. Err. [90% Conf. Interval] -------------+------------------------------------------------------------- | 5999 .296216 .005895 .2865107 .3060676 . cii 12 27, poisson -- Poisson Exact -- Variable | Exposure Mean Std. Err. [95% Conf. Interval] -------------+------------------------------------------------------------- | 12 2.25 .4330127 1.483144 3.273587 1.2. KiÓm ®Þnh gi¶ thuyÕt thèng kª 1.2.1. KiÓm ®Þnh gi¸ trÞ trung b×nh cña mÉu Ph©n phèi kh«ng mét Có ph¸p: prtest <biÕn>= # [®iÒu kiÖn] [ph¹m vi] [, level(#)] LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ tû lÖ gi¸ trÞ cña biÕn ph©n phèi theo quy luËt kh«ng mét (Ho: p = p0). VÝ dô: . prtest poor=0.44 if reg7==1 One-sample test of proportion poor: Number of obs = 859 ---------------------------------------------------------------------------- Variable | Mean Std. Err. z P>|z| [95% Conf. Interval] ---------+------------------------------------------------------------------ poor | .4982538 .0170597 29.2065 0.0000 .4648174 .5316901 ---------------------------------------------------------------------------- Ho: proportion(poor) = .44 Ha: poor < .44 Ha: poor ~= .44 Ha: poor > .44 z = 3.440 z = 3.440 z = 3.440 P < z = 0.9997 P > |z| = 0.0006 P > z = 0.0003 prtest <biÕn 1> = <tªn biÕn2> [®iÒu kiÖn] [ph¹m vi] [, level(#)] LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña tû lÖ cña hai gi¸ trÞ biÕn ®−îc chØ ra bëi tªn biÕn (Ho: pX = pY).
- 46. 46 VÝ dô: KiÓm®Þnh xem tû lÖ nghÌo ®ãi gi÷a vïng 2 v vïng 4 cã khac nhau kh«ng: . gen poor2=poor if reg7==2 (4824 missing values generated) . gen poor4=poor if reg7==4 (5245 missing values generated) . prtest poor2 = poor4 Two-sample test of proportion poor2: Number of obs = 1175 poor4: Number of obs = 754 ------------------------------------------------------------------------------ Variable | Mean Std. Err. z P>|z| [95% Conf. Interval] ---------+-------------------------------------------------------------------- poor2 | .2365957 .0123983 19.0829 0.0000 .2122955 .2608959 poor4 | .2864721 .016465 17.3989 0.0000 .2542014 .3187429 ---------+-------------------------------------------------------------------- diff | -.0498764 .020611 -.0902732 -.0094796 | under Ho: .0203666 -2.44893 0.0143 ------------------------------------------------------------------------------ Ho: proportion(poor2) - proportion(poor4) = diff = 0 Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 z = -2.449 z = -2.449 z = -2.449 P < z = 0.0072 P > |z| = 0.0143 P > z = 0.9928 prtest <biÕn> [®iÒu kiÖn] [ph¹m vi], by(biÕn ph©n nhãm) [level(#)] LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña tû lÖ cña hai nhãm ®−îc chØ ra bëi biÕn ph©n nhãm (Ho: pX1 = pX2). VÝ dô: . prtest poor, by(sex) Two-sample test of proportion 1: Number of obs = 4375 2: Number of obs = 1624 ------------------------------------------------------------------------------ Variable | Mean Std. Err. z P>|z| [95% Conf. Interval] ---------+-------------------------------------------------------------------- 1 | .3248 .00708 45.8755 0.0000 .3109234 .3386766 2 | .2192118 .0102661 21.353 0.0000 .1990906 .239333 ---------+-------------------------------------------------------------------- diff | .1055882 .0124708 .0811459 .1300304 | under Ho: .0132673 7.95855 0.0000 ------------------------------------------------------------------------------ Ho: proportion(1) - proportion(2) = diff = 0 Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 z = 7.959 z = 7.959 z = 7.959 P < z = 1.0000 P > |z| = 0.0000 P > z = 0.0000
- 47. 47 Ph©n phèi nhÞthøc Có ph¸p: bitest <biÕn> = #p [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] LÖnh n y kiÓm ®Þnh gi¶ thuyÕt vÒ tham sè p trong quy luËt nhÞ thøc (x¸c suÊt th nh c«ng cña phÐp thö) cña biÕn ®−îc chØ ra bëi tªn biÕn. (Ho: p = p0) VÝ dô: . bitest poor=0.44 if reg7==1 Variable | N Observed k Expected k Assumed p Observed p -------------+------------------------------------------------------------ poor | 859 428 377.96 0.44000 0.49825 Pr(k >= 428) = 0.000344 (one-sided test) Pr(k <= 428) = 0.999732 (one-sided test) Pr(k <= 328 or k >= 428) = 0.000660 (two-sided test) . bitesti 859 428 0.44 N Observed k Expected k Assumed p Observed p ------------------------------------------------------------ 859 428 377.96 0.44000 0.49825 Pr(k >= 428) = 0.000344 (one-sided test) Pr(k <= 428) = 0.999732 (one-sided test) Pr(k <= 328 or k >= 428) = 0.000660 (two-sided test) Quy luËt ph©n phèi chuÈn Có ph¸p: ttest <biÕn> = # [®iÒu kiÖn] [ph¹m vi] [, level(#) ] LÖnh n y kiÓm ®Þnh gi¶ thuyÕt vÒ gi¸ trÞ cña tham sè trung b×nh cña biÕn ngÉu nhiªn tu©n theo quy luËt chuÈn ®−îc chØ ra bëi tªn biÕn (Ho: µ = µ0) VÝ dô: . ttest rlpcex1=3200 One-sample t test ------------------------------------------------------------------------------ Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- rlpcex1 | 5999 3188.667 34.76379 2692.567 3120.518 3256.817 ------------------------------------------------------------------------------ Degrees of freedom: 5998 Ho: mean(rlpcex1) = 3200 Ha: mean < 3200 Ha: mean ~= 3200 Ha: mean > 3200 t = -0.3260 t = -0.3260 t = -0.3260 P < t = 0.3722 P > |t| = 0.7444 P > t = 0.6278
- 48. 48 ttest <biÕn 1>= <biÕn 2> [®iÒu kiÖn] [ph¹m vi] [, unpaired unequal level(#) ] LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt r»ng hai biÕn cã gi¸ trÞ trung b×nh b»ng nhau. (Ho: µX = µY). C¸c tuú chän: unpaired Sè liÖu cña hai biÕn kh«ng cïng cÆp unequal Phu¬ng sai cña hai biÕn kh«ng b»ng nhau VÝ dô: . ttest poor2=poor4, unpaired unequal Two-sample t test with unequal variances ------------------------------------------------------------------------------ Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- poor2 | 1175 .2365957 .0124036 .425173 .2122601 .2609314 poor4 | 754 .2864721 .0164759 .4524128 .254128 .3188163 ---------+-------------------------------------------------------------------- combined | 1929 .2560912 .0099404 .436586 .2365962 .2755863 ---------+-------------------------------------------------------------------- diff | -.0498764 .0206229 -.0903285 -.0094243 ------------------------------------------------------------------------------ Satterthwaite's degrees of freedom: 1532.64 Ho: mean(poor2) - mean(poor4) = diff = 0 Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 t = -2.4185 t = -2.4185 t = -2.4185 P < t = 0.0079 P > |t| = 0.0157 P > t = 0.9921 ttest <biÕn> [®iÒu kiÖn] [ph¹m vi], by(biÕn ph©n nhãm) [ unequal level(#) ] LÖnh n y thùc hiÖn kiÓm ®Þnh gi¶ thuyÕt vÒ sù b»ng nhau cña gi¸ trÞ trung b×nh cña hai nhãm ®−îc chØ ra bëi biÕn ph©n nhãm (Ho: µX1 = µX2). VÝ dô: . ttest rlpcex1, by(sex) Two-sample t test with equal variances ------------------------------------------------------------------------------ Group | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- 1 | 4375 2980.906 36.74795 2430.648 2908.862 3052.951 2 | 1624 3748.368 80.18189 3231.241 3591.097 3905.638 ---------+-------------------------------------------------------------------- combined | 5999 3188.667 34.76379 2692.567 3120.518 3256.817 ---------+-------------------------------------------------------------------- diff | -767.4613 77.6155 -919.6156 -615.3071 ------------------------------------------------------------------------------ Degrees of freedom: 5997
- 49. 49 Ho: mean(1) -mean(2) = diff = 0 Ha: diff < 0 Ha: diff ~= 0 Ha: diff > 0 t = -9.8880 t = -9.8880 t = -9.8880 P < t = 0.0000 P > |t| = 0.0000 P > t = 1.0000 1.2.2. KiÓm ®Þnh gi¸ trÞ ®é lÖch chuÈn Có ph¸p: sdtest <biÕn> = # [®iÒu kiÖn] [ph¹m vi] [, level(#) ] sdtest <biÕn 1> = <biÕn 2> [®iÒu kiÖn] [ph¹m vi] [, level(#) ] sdtest <biÕn> [®iÒu kiÖn] [ph¹m vi] , by(biÕn ph©n nhãm) [ level(#) ] LÖnh n y kiÓm dÞnh tham sè ®é lÖch chuÈn cña biÕn ngÉu nhiªn tu©n theo quy luËt chuÈn ®−îc chØ ra bëi tªn biÕn. Có ph¸p cña lÖn n y t−¬ng tù víi có ph¸p cña lÖnh ttest VÝ dô: . sum rlpcex1 Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- rlpcex1 | 5999 3188.667 2692.567 357.318 45801.71 . sdtest rlpcex1=2700 One-sample test of variance ------------------------------------------------------------------------------ Variable | Obs Mean Std. Err. Std. Dev. [95% Conf. Interval] ---------+-------------------------------------------------------------------- rlpcex1 | 5999 3188.667 34.76379 2692.567 3120.518 3256.817 ------------------------------------------------------------------------------ Ho: sd(rlpcex1) = 2700 chi2(5998) = 5965.022 Ha: sd(rlpcex1) < 2700 Ha: sd(rlpcex1) ~= 2700 Ha: sd(rlpcex1) > 2700 P < chi2 = 0.3838 2*(P < chi2) = 0.7676 P > chi2 = 0.6162 2. Ph©n tÝch t−¬ng quan v håi quy (Correlation and regression) 2.1. Ph©n tÝch t−¬ng quan Có ph¸p: correlate [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, means covariance _coef wrap] LÖnh n y tÝnh ma trËn hÖ sè t−ong quan (correlation coefficient), hoÆc hiÖp ph−¬ng sai (covariance) cho c¸c biÕn ®−îc liÖt kª trong danh s¸ch biÕn. Sè quan s¸t ®−îc dïng l sè quan s¸t cña biÕn cã Ýt quan s¸t nhÊt. C¸c tuú chän:
- 50. 50 means HiÓn thÞc¸c thèng kª kh¸c nh− gi¸ trÞ trung b×nh, ®é lÖch chuÈn, gi¸ trÞ lín nhÊt, nhá nhÊt covariance §−a ra ma trËn hiÖp ph−¬ng sai thay v× hÖ sè t−¬ng quan _coef TÝnh ma trËn tu¬ng quan cña c¸c hÖ sè cña −íc l−îng gÇn nhÊt wrap HiÓn thÞ c¸c dßng cña ma trËn liÒn nhau nÕu cã qua nhiÒu c¸c biÕn ®−îc liÖt kª VÝ dô: . corr hhsize poor rlpcex1 sex (obs=5999) | hhsize poor rlpcex1 sex -------------+------------------------------------ hhsize | 1.0000 poor | 0.2425 1.0000 rlpcex1 | -0.2172 -0.4452 1.0000 sex | -0.2570 -0.1028 0.1267 1.0000 . corr hhsize poor rlpcex1 sex, means cov (obs=5999) Variable | Mean Std. Dev. Min Max -------------+---------------------------------------------------- hhsize | 4.752292 1.954292 1 19 poor | .296216 .4566255 0 1 rlpcex1 | 3188.667 2692.567 357.318 45801.71 sex | 1.270712 .4443645 1 2 | hhsize poor rlpcex1 sex -------------+------------------------------------ hhsize | 3.81926 poor | .216435 .208507 rlpcex1 | -1142.93 -547.335 7.2e+06 sex | -.223195 -.020849 151.543 .19746 pwcorr [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, obs sig print(#) star(#)] LÖnh n y tÝnh hÖ sè t−¬ng quan cho tõng cÆp biÕn ®−îc chØ ra bëi danh s¸ch biÕn. C¸c tuú chän: obs HiÓn thÞ sè quan s¸t dïng ®Ó tÝnh hÖ sè t−¬ng quan sig HiÓn thÞ møc ý nghÜa cña c¸c hÖ sè t−¬ng quan print(#) ChØ ra møc ý nghÜa theo ®ã chØ c¸c hÖ sè t−¬ng quan cã møc ý nghÜa nhá h¬n møc n y míi ®−îc hiÓn thÞ star(#) §¸nh dÊu sao ®èi víi c¸c hÖ sè t−¬ng quan cã møc ý nghÜ nhá h¬n
- 51. 51 møc ®−îc chØra bëi star VÝ dô: . pwcorr hhsize poor rlpcex1 sex, obs sig star(5) | hhsize poor rlpcex1 sex -------------+------------------------------------ hhsize | 1.0000 | | 5999 | poor | 0.2425* 1.0000 | 0.0000 | 5999 5999 | rlpcex1 | -0.2172* -0.4452* 1.0000 | 0.0000 0.0000 | 5999 5999 5999 | sex | -0.2570* -0.1028* 0.1267* 1.0000 | 0.0000 0.0000 0.0000 | 5999 5999 5999 5999 | pcorr <biÕn> <danh s¸ch biÕn> [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] LÖnh n y tÝnh hÖ sè t−¬ng quan cña biÕn ®−îc chØ ra bëi tªn biÕn víi c¸c biÕn ®−îc trong danh s¸ch biÕn VÝ dô: . pwcorr poor hhsize rlpcex1 sex | poor hhsize rlpcex1 sex -------------+------------------------------------ poor | 1.0000 hhsize | 0.2425 1.0000 rlpcex1 | -0.4452 -0.2172 1.0000 sex | -0.1028 -0.2570 0.1267 1.0000 2.2. Ph©n tÝch håi quy Ph−¬ng ph¸p b×nh ph−¬ng nhá nhÊt (Ordinary-Least Square) Có ph¸p: regress <biÕn phô thuéc> [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, option] LÖnh n y −íc l−îng c¸c hÖ sè cña h m biÕn phô thuéc (dependent variable) theo c¸c biÕn ®éc lËp (danh s¸ch biÕn) theo ph−¬ng ph¸p b×nh ph−¬ng nhá nhÊt. VÝ dô:
- 52. 52 . reg rlpcex1reg7 sex hhsize Source | SS df MS Number of obs = 5999 -------------+------------------------------ F( 3, 5995) = 194.88 Model | 3.8639e+09 3 1.2880e+09 Prob > F = 0.0000 Residual | 3.9621e+10 5995 6609032.15 R-squared = 0.0889 -------------+------------------------------ Adj R-squared = 0.0884 Total | 4.3485e+10 5998 7249918.40 Root MSE = 2570.8 ------------------------------------------------------------------------------ rlpcex1 | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- reg7 | 240.9633 15.5905 15.46 0.000 210.4003 271.5263 sex | 403.2984 77.38324 5.21 0.000 251.5994 554.9974 hhsize | -305.6382 17.70692 -17.26 0.000 -340.3501 -270.9263 _cons | 3160.201 155.6576 20.30 0.000 2855.056 3465.346 ------------------------------------------------------------------------------ C¸c tuú chän: level(#) ChØ ra møc tin cËy cho −íc l−îng kho¶ng tin cËy cña hÖ sè noconstant Kh«ng cã hÖ sè (intercept) trong h m håi quy noheader ChØ hiÓn thÞ kÕt qu¶ ph©n tÝch vÒ c¸c hÖ sè beta HiÓn thÞ hÖ sè ®−îc chuÈn ho¸, dïng ®Ó so s¸nh møc ®é ¶nh h−ëng cña c¸c hÖ sè víi nhau Ph−¬ng ph¸p kh¶ n¨ng lín nhÊt (Maximum-Likelihood) Có ph¸p: probit <biÕn phô thuéc> [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, tuú chän] LÖnh n y thùc hiÖn håi quy biÕn phô thuéc theo c¸c biÕn ®−îc chØ ra trong danh s¸ch biÕn theo ph−¬ng ph¸p kh¶ n¨ng lín nhÊt. BiÕn phô thuéc th−êng l biÕn gi¶ víi hai gi¸ trÞ 0 v 1. VÝ dô: . probit poor reg7 sex hhsize Iteration 0: log likelihood = -3645.1363 Iteration 1: log likelihood = -3367.2185 Iteration 2: log likelihood = -3364.8032 Iteration 3: log likelihood = -3364.8025 Probit estimates Number of obs = 5999 LR chi2(3) = 560.67 Prob > chi2 = 0.0000 Log likelihood = -3364.8025 Pseudo R2 = 0.0769 ------------------------------------------------------------------------------ poor | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- reg7 | -.116342 .0084551 -13.76 0.000 -.1329136 -.0997703 sex | -.1284525 .0422247 -3.04 0.002 -.2112113 -.0456937 hhsize | .1808115 .0095806 18.87 0.000 .1620338 .1995892 _cons | -.8088731 .0824798 -9.81 0.000 -.9705306 -.6472157 ------------------------------------------------------------------------------
- 53. 53 ¦íc l−îng gi¸trÞ biÕn phô thuéc v phÇn d− Có ph¸p: predict <tªn biÕn míi> [®iÒu kiÖn] [ph¹m vi] [, xb stdp resid] LÖnh n y ®−îc thùc hiÖn sau lÖnh regress (hoÆc probit) ®Ó t¹o ra 1 biÕn míi cã gi¸ trÞ ®−îc tÝnh tuú theo tuú chän ®−îc chØ ra. C¸c tuú chän: xb cho phÐp −íc l−îng gi¸ trÞ cña biÕn phô thuéc thu ®−îc tõ h m håi quy: i10i XˆˆYˆ β+β= stdp −íc l−îng sai sè chuÈn cña gia trÞ −íc l−îng: ),(CovX2)ˆ(VarX)(VarSE 10i1 2 i0i ββ−β+β= redid −íc l−îng gi¸ trÞ phÇn d−: iii YˆYe −= VÝ dô: predict exphat, xb T¹o ra biÕn míi exphat cã gi¸ trÞ −íc l−îng cña biÕn phô thuéc (fitted value) theo hÖ sè thu ®−îc tõ h m håi quy. predict expres, resid T¹o ra biÕn expres cã gi¸ trÞ cña phÇn d−. KiÓm ®Þnh vÒ hÖ sè cña h m håi quy Có ph¸p: test [gi¸ trÞ biÓu thøc] test [danh s¸ch biÕn] testparm <danh s¸ch biÕn> [, equal ] LÖnh test kiÓm ®Þnh c¸c gi¶ thiÕt vÒ hÖ sè cña h m håi quy võa míi ®−îc −íc l−îng VÝ dô: test urban98 =2000 KiÓm ®Þnh gi¶ thiÕt hÖ sè cña biÕn urban98 = 0 test region1 = region2 KiÓm ®Þnh gi¶ thiÕt hÖ sè cña biÕn region1 b»ng hÖ sè cña biÕn region2 test region1 = (region2+region3)/2 KiÓm ®Þnh gi¶ thiÕt vÒ quan hÖ gi÷a c¸c hÖ sè cña biÕn region1, region2, va region3 test region1 region2 region3
- 54. 54 KiÓm ®Þnh gi¶thiÕt hÖ sè cña biÕn region1, region2, va region3 ®Òu b»ng 0 testparm region* KiÓm ®Þnh gi¶ thiÕt vÒ cña hÖ sè cña biÕn region1 ®Õn region7 ®Òu b»ng 0 . tab reg7, gen(region) Code by 7 | regions | Freq. Percent Cum. ------------+----------------------------------- region1 | 859 14.32 14.32 region2 | 1175 19.59 33.91 region3 | 708 11.80 45.71 region4 | 754 12.57 58.28 region5 | 368 6.13 64.41 region6 | 1023 17.05 81.46 region7 | 1112 18.54 100.00 ------------+----------------------------------- Total | 5999 100.00 . reg rlpcex1 urban98 region* sex educyr98 hhsize Source | SS df MS Number of obs = 5999 -------------+------------------------------ F( 10, 5988) = 382.87 Model | 1.6960e+10 10 1.6960e+09 Prob > F = 0.0000 Residual | 2.6525e+10 5988 4429712.49 R-squared = 0.3900 -------------+------------------------------ Adj R-squared = 0.3890 Total | 4.3485e+10 5998 7249918.40 Root MSE = 2104.7 ------------------------------------------------------------------------------ rlpcex1 | Coef. Std. Err. t P>|t| [95% Conf. Interval] -------------+---------------------------------------------------------------- urban98 | 1995.163 66.46943 30.02 0.000 1864.859 2125.467 region1 | -923.7066 132.8334 -6.95 0.000 -1184.108 -663.3052 region2 | -362.6047 130.2254 -2.78 0.005 -617.8934 -107.316 region3 | -558.0354 137.1551 -4.07 0.000 -826.9089 -289.1619 region4 | -100.7586 135.8372 -0.74 0.458 -367.0486 165.5313 region5 | (dropped) region6 | 1742.688 131.9928 13.20 0.000 1483.934 2001.441 region7 | 151.9854 128.0272 1.19 0.235 -98.99396 402.9648 sex | 270.9142 66.61031 4.07 0.000 140.3339 401.4944 educyr98 | 153.3281 6.836934 22.43 0.000 139.9253 166.731 hhsize | -257.691 14.73741 -17.49 0.000 -286.5816 -228.8004 _cons | 2362.355 178.3197 13.25 0.000 2012.784 2711.926 ------------------------------------------------------------------------------ . test urban98 =2000 ( 1) urban98 = 2000.0 F( 1, 5988) = 0.01 Prob > F = 0.9420 . test region1 = region2 ( 1) region1 - region2 = 0.0 F( 1, 5988) = 34.57
- 55. 55 Prob > F= 0.0000 . test region1 = (region2+region3)/2 ( 1) region1 - .5 region2 - .5 region3 = 0.0 F( 1, 5988) = 27.80 Prob > F = 0.0000 . test region1 region2 region3 ( 1) region1 = 0.0 ( 2) region2 = 0.0 ( 3) region3 = 0.0 F( 3, 5988) = 20.22 Prob > F = 0.0000 . testparm region* ( 1) region1 = 0.0 ( 2) region2 = 0.0 ( 3) region3 = 0.0 ( 4) region4 = 0.0 ( 5) region5 = 0.0 ( 6) region6 = 0.0 ( 7) region7 = 0.0 Constraint 5 dropped F( 6, 5988) = 148.55 Prob > F = 0.0000 Ch−¬ng IV: VÏ ®å thÞ 1. VÏ ®å thÞ (graph) Có ph¸p:
- 56. 56 graph [danh s¸chbiÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi] [, lo¹i_®å_thÞ tuú_chän_riªng tuú_chän_chung] Trong ®ã: lo¹i_®å_thÞ (graph_type) ChØ ra lo¹i ®å thÞ cÇn vÏ tuú_chän_riªng (specific_options) C¸c tuú chän liªn quan ®Õn tõng lo¹i ®å thÞ tuú_chän_chung (common_options) C¸c tuú chän cã thÓ sö dông chung cho c¸c lo¹i ®å thÞ nh− tuú chän vÒ ®¸nh nh n trªn c¸c trôc cña ®å thÞ Stata cho phÐp vÏ 8 lo¹i ®å thÞ nh− sau (graph_type): (1) §å thÞ 2 chiÒu (two-way scatterplots) . graph rlpcex1 age comp.M&Regpriceadj.pctotexp Age of household head 16 95 357.318 45801.7 (2) Ma trËn ®å thÞ 2 chiÒu (two-way scatterplot matrices) . gr rlpcex1 age educyr98 hhsize, matrix
- 57. 57 comp.M&Reg price adj.pc totexp 16 95 357.318 45801.7 1 19 16 95 Age of household head schooling year of HH.head 0 22 357.318 45801.7 1 19 0 22 Household size (3) §å thÞ tÇn suÊt (histograms) . gr rlpcex1, bin(50) normal Fraction comp.M&Reg price adj.pc tot exp 357.318 45801.7 0 .329888 (4) §å thÞ r¶i mét chiÒu (one-way scatterplots) . gr rlpcex1, oneway
- 58. 58 comp.M&Reg price adj.pctot exp357.318 45801.71 (5) §å thÞ h×nh hép (box-and-whisker plots) 357.318 45801.7 comp.M&Reg price adj.pc tot exp (6) §å thÞ cét (bar chart) . sort reg7 . gr poor, bar means by(reg7)
- 59. 59 0 .498254 poor 1 2 34 5 6 7 (7) §å thÞ h×nh trßn (pie charts) . for num 1/7: gen poorX=poor if reg7==X -> gen poor1=poor if reg7==1 (5140 missing values generated) -> gen poor2=poor if reg7==2 (4824 missing values generated) -> gen poor3=poor if reg7==3 (5291 missing values generated) -> gen poor4=poor if reg7==4 (5245 missing values generated) -> gen poor5=poor if reg7==5 (5631 missing values generated) -> gen poor6=poor if reg7==6 (4976 missing values generated) -> gen poor7=poor if reg7==7 (4887 missing values generated) . graph poor1-poor7, pie
- 60. 60 24% poor1 16% poor2 16%poor3 12% poor4 10% poor5 4% poor6 18% poor7 (8) §å thÞ h×nh sao (star charts) chart_type l star Price Mileage (mpg) Repair Record 1978 Headroom (in.) Trunk space (cu. ft.) Weight (lbs.) Length (in.) Turn Circle (ft.) Displacement (cu. in.) Audi 5000 Audi Fox BMW 320i Datsun 200 Datsun 210 Datsun 510 Datsun 810 Fiat Strada Honda Accord Honda Civic Mazda GLC Renault Subaru Toyota Celica Toyota Corolla Toyota Corona VW Dasher VW Diesel VW Rabbit VW Scirocco Volvo 260 C¸c lùa chän chung (common_options) * T¹o tÖp sè liÖu . tabulate hhsize, sum (rlpcex1) | Summary of comp.M&Reg price adj.pc Household | tot exp size | Mean Std. Dev. Freq. ------------+------------------------------------ 1 | 4696.0254 4619.5012 214
- 61. 61 2 | 4131.48923677.2297 497 3 | 3834.8615 2913.8177 731 4 | 3428.8011 2599.7301 1404 5 | 2930.5486 2168.0644 1318 6 | 2626.6848 2277.1893 867 7 | 2501.0912 2186.1605 480 8 | 2329.7009 1803.7873 255 9 | 2207.0166 1380.5607 126 10 | 2252.3772 1423.7576 58 11 | 2370.7034 1404.7148 29 12 | 1747.3691 924.72977 9 13 | 2114.1337 2109.0077 4 14 | 1579.78 990.81152 4 16 | 2994.5771 2061.6804 2 19 | 4833.936 0 1 ------------+------------------------------------ Total | 3188.6671 2692.5673 5999 . tab hhsize, sum(educyr98) | Summary of schooling year of Household | HH.head size | Mean Std. Dev. Freq. ------------+------------------------------------ 1 | 3.7897196 4.3956537 214 2 | 5.7545272 4.7225549 497 3 | 7.3023256 4.6396425 731 4 | 8.2578348 4.2659841 1404 5 | 7.7243298 4.2998488 1318 6 | 6.8788927 4.0778062 867 7 | 6.3348958 4.1241759 480 8 | 5.7333333 3.9623557 255 9 | 5.7936508 3.4878474 126 10 | 6.1724138 3.1851516 58 11 | 4.7931034 3.1665586 29 12 | 4.4444444 3.6438685 9 13 | 5 5.0990195 4 14 | 3 2.1602469 4 16 | 4 1.4142136 2 19 | 2 0 1 ------------+------------------------------------ Total | 7.0944185 4.4160917 5999 . replace meanexp= meanexp/1000 (16 real changes made) . replace meanexp= meanexp/1000 . rename var71 ahhsize . rename var72 meanexp . rename var73 meanedu . replace meanexp= meanexp/1000 . label var meanexp “Chi tieu binh quan” . label var meanedu “So nam hoc” . label var ahhsize “Quy mo ho” * C¸c tuú chän vÒ tiªu ®Ò v trôc to¹ ®é LÊy vÝ dô ®å thÞ 2 chiÒu, trôc tung thÓ hiÖn chi tiªu b×nh qu©n v sè n¨m häc b×nh qu©n cña chñ hé, trôc ho nh thÓ hiÖn quy m« hé gia ®×nh. . gr meanexp meanedu ahhsize
- 62. 62 ahhsize meanexp meanedu 1 19 1.57978 8.25783 *Lùa chän vÒ tiªu ®Ò: title("chuçi ký tù") t1title("chuçi ký tù") t2title("chuçi ký tù") b1title("chuçi ký tù") b2title("chuçi ký tù") l1title("chuçi ký tù") l2title("chuçi ký tù") r1title("chuçi ký tù") r2title("chuçi ký tù") LÖnh n y ghi c¸c tiªu ®Ò trªn phÝa trªn (top), phÝa d−íi (bottom), bªn tr¸i (left) v bªn ph¶i (right) ®å thÞ. VÝ dô: gr meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) Chitieubinhquan(trdong) Sonamhoccuachuho Do thi chi tieu va hoc van chu ho Quy mo ho gia dinh Chi tieu binh quan So nam hoc 1 19 1.57978 8.25783
- 63. 63 * HiÓn thÞgi¸ trÞ trôc ®å thÞ xlabel[(gi¸ trÞ sè)] ylabel[(gi¸ trÞ sè)] rlabel[(gi¸ trÞ sè)] tlabel[(gi¸ trÞ sè)] VÝ dô: gr meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel Chitieubinhquan(trdong) Sonamhoccuachuho Do thi chi tieu va hoc van chu ho Quy mo ho gia dinh Chi tieu binh quan So nam hoc 0 5 10 15 20 2 4 6 8 Chó ý: C¸c lùa chän kh¸c cã thÓ xem ë phÇn help b»ng lÖnh: help graxes C¸c tuú chän vÒ ®−êng nèi xline[(gi¸ trÞ sè)] yline[(gi¸ trÞ sè)] rline[(gi¸ trÞ sè)] tline[(gi¸ trÞ sè)] connect(c[[p]] ... c[[p]]) VÝ dô: . gr meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel xline (5 10 to 20) yline(2 4 to 8) connect(ll)
- 64. 64 Chitieubinhquan(trdong) Sonamhoccuachuho Do thi chitieu va hoc van chu ho Quy mo ho gia dinh Chi tieu binh quan So nam hoc 0 5 10 15 20 2 4 6 8 2. Mét sè lo¹i ®å thÞ th−êng dïng 2.1. §å thÞ 2 chiÒu Có ph¸p: graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], twoway [tuú_chän_chung rescale] Tuú chän rescale cho phÐp hiÖn thÞ hai trôc tung víi gi¸ trÞ kh¸c nhau . gen meanexp1=meanexp*1000 . label var meanexp1 "Chi tieu binh quan" . gr meanexp1 meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (nghin dong)) b2title (Quy mo ho gia dinh) xlabel ylabel rlabel(2 4 to 8) connect(ll) rescale
- 65. 65 Chitieubinhquan(nghindong) Do thi chitieu va hoc van chu ho Quy mo ho gia dinh Sonamhoc Chi tieu binh quan So nam hoc 0 5 10 15 20 1000 2000 3000 4000 5000 2 4 6 8 2.2. §å thÞ tÇn suÊt Có ph¸p: graph [biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], histogram [tuú_chän_chung bin(#) freq normal[(#,#)] density(#)] C¸c tuú chän: bin(#) ChØ ra sè l−îng kho¶ng cho ®å thÞ, gi¸ trÞ ngÇm ®Þnh l bin(5) Freq Gi¸ trÞ tÇn suÊt sÏ ®−îc hiÓn thÞ trªn trôc tung normal[(#,#)] VÏ h m ph©n phèi chuÈn density(#)] §−îc dïng víi lùa chän normal, chØ ra sè l−îng ®iÓm ®Ó −íc l−îng h m mËt ®é theo ph©n phèi chuÈn VÝ dô: §å thÞ tÇn suÊt cña chi tiªu binh qu©n ®Çu ng−êi . gr rlpcex1, hist bin(20) normal
- 66. 66 Fraction comp.M&Reg price adj.pctot exp 357.318 45801.7 0 .56026 . gr rlpcex1, hist bin(50) normal freq Frequency comp.M&Reg price adj.pc tot exp 357.318 45801.7 0 1979 . gr rlpcex1, hist bin(50) normal freq by(reg7)
- 67. 67 Frequency Histograms by Codeby 7 regions comp.M&Reg price adj.pc tot exp region1 0 415 region2 region3 region4 0 415 region5 357.318 45801.7 region6 357.318 45801.7 region7 357.318 45801.7 0 415 2.3. §å thÞ h×nh cét Có ph¸p: graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], bar [tuú_chän_chung [no]alt means stack] VÝ dô: §å thÞ gi¸ trÞ trung b×nh häc vÊn cña chñ hé v quy m« hé gia ®×nh theo 7 vïng . gr educyr98 hhsize, bar means by(reg7) 0 8.64426 schooling year of HH.head Household size 1 2 3 4 5 6 7 . label define region 1 "region1" 2 "region2" 3 "region3" 4 "region4" 5 "region5" 6 "region6" 7 "region7"
- 68. 68 . label valuesreg7 region . tab reg7 Code by 7 | regions | Freq. Percent Cum. ------------+----------------------------------- region1 | 859 14.32 14.32 region2 | 1175 19.59 33.91 region3 | 708 11.80 45.71 region4 | 754 12.57 58.28 region5 | 368 6.13 64.41 region6 | 1023 17.05 81.46 region7 | 1112 18.54 100.00 ------------+----------------------------------- Total | 5999 100.00 . gr educyr98 hhsize, bar means by(reg7) ylabel( 2 4 to 10) alt 2 4 6 8 10 schooling year of HH.head Household size region1 region2 region3 region4 region5 region6 region7 Lùa chän stack . gen persons=1 . gr persons urban98, bar ylabel by(reg7) stack alt
- 69. 69 0 500 1000 1500 persons 1:urban 98;0:rural 98 region1 region2 region3 region4 region5 region6 region7 VÝ dô: H y vÔ ®å thÞ sau: 0 200 400 600 foodpoor poor region1 region2 region3 region4 region5 region6 region7 2.4. §å thÞ h×nh trßn Có ph¸p: graph [danh s¸ch biÕn] [quyÒn sè] [®iÒu kiÖn] [ph¹m vi], pie [tuú_chän_chung] LÖnh n y vÏ ®å thÞ h×nh trßn Mèi biÕn sÏ chiÕm 1 phÇn cña h×nh trßn v tû lÖ cña phÇn n y do tæng gi¸ trÞ cña c¸c quan s¸t cu¶ biÕn ®ã quyÕt ®Þnh. VÝ dô: VÏ ®å thÞ tû lÖ phÇn tr¨m sè ng−êi nghÌo cña mçi vïng trªn tæng sè ng−êi nghÌo cña c¶ n−íc. . gr poor1-poor7, pie
- 70. 70 24% poor1 16% poor2 16%poor3 12% poor4 10% poor5 4% poor6 18% poor7 . gen nonfpood=poor- foodpoor . label var nonfpood "poor but still above food poverty line" . gen nonpoor=( rlpcex1>=1790) . gr foodpoor nonfpood nonpoor, pie . set textsize 90 12% foodpoor 18% poor but still above food povert 70% nonpoor . set textsize 100 . gr foodpoor nonfpood nonpoor, pie by(reg7) total
- 71. 71 12% foodpoor 18% poorbut still above food povert 70% nonpoor region1 region2 region3 region4 region5 region6 region7 Total 3. L−u tr÷ v hiÓn thÞ ®å thÞ (Saving and graph using) §Ó l−u tr÷ ®å thÞ th× t¹i cöa sæ graph, v o thùc ®¬n File, chän Save graph, sau ®ã lùa chän ®−êng dÉn v tªn file cho ®å thÞ, phÇn më réng ngÇm ®Þnh l gph. §å thÞ còng cã thÓ ®−îc l−u tr÷ b»ng tuú chän saving(tªn tÖp [,replace]) viÕt sau lÖnh graph VÝ dô: . gr educyr98 hhsize, bar means by(reg7) ylabel( 2 4 to 10) alt saving ("c: do thi 1") . gr persons urban98, bar ylabel by(reg7) stack alt saving("c:do thi 2") §Ó kh«ng hiÓn thÞ ®å thÞ th× cã thÓ dïng lÖnh t¾t chÕ ®é hiÓn thÞ ®å thÞ b»ng lÖnh set graphics { on | off } . set graphics off . gr poor1-poor7, pie saving ("c:do thi 3", replace) (note: file c:do thi 3.gph not found) Stata cho phÐp hiÓn thÞ c¸c ®å thÞ ® l−u tr÷ b»ng lÖnh: graph using <tÖp tÖp ®å thÞ 1> [tÖp tÖp ®å thÞ 2 ...] [, margin(#)] margin(#) chØ ra kho¶ng c¸ch lÒ bao quanh ®å thÞ theo gi¸ trÞ phÇn tr¨m cña diÖn tÝch ®å thÞ. Gi¸ trÞ ngÇm ®Þnh l 0. VÝ dô: . set graphics on
- 72. 72 . graph using"c:do thi 1" "c:do thi 2" "c:do thi 3", margin(10) title("Mot so dac diem cua ho gia dinh") Mot so dac diem cua ho gia dinh 12% foodpoor 18% poor but still above food povert 70% nonpoor region1 region2 region3 region4 region5 region6 region7 Total 0 500 1000 1500 persons 1:urban 98; 0:rural 98 region1 region2 region3 region4 region5 region6 region7 24% poor1 16% poor2 16% poor3 12% poor4 10% poor5 4% poor6 18% poor7 Chó ý: Chóng ta co thÓ kÕt hîp lÖnh saving víi using ®Ó l−u tr÷ ra ®å thÞ míi. VÝ dô: . graph using "c:do thi 1" "c:do thi 2" "c:do thi 3", margin(10) title("Mot so dac die m cua ho gia dinh") saving("c:do thi tong hop") . graph using "c:do thi tong hop"
- 73. 73 Ch−¬ng V: LËptr×nh trong Stata 1. Giíi thiÖu chung vÒ ch−¬ng tr×nh do-file 1.1. Më v l−u tr÷ do-file Stata cho phÐp viÕt c¸c tÖp ®−îc gäi l do-file bao gåm c¸c lÖnh cña Stata. Thay v× thùc hiÖn tõng lÖnh mét tõ cöa sæ lÖnh command, c¸c tÖp do-file sÏ lÇn l−ît thùc hiÖn c¸c lÖnh ®ã. Ch−¬ng tr×nh Stata ®−îc so¹n th¶o trong cöa sæ do-file editor. Cöa sæ n y ®−îc më b»ng c¸ch kÝch v o thùc ®¬n Windows v chän tuú chän do-file editor. Mét c¸ch kh¸c ®Ó më cöa sæ n y l gâ lÖnh doedit t¹i cöa sæ lÖnh command. VÝ dô: Mét ch−¬ng tr×nh cã thÓ ®−îc so¹n th¶o trong cöa sæ do-file editor nh− sau: ---------------- clear set mem 32m use "C:VLSS98Hhexp98n.dta", clear tab urban98 sum hhsize gen new=hhsizet gen new=hhsize ---------------- Sau khi so¹n th¶o, do-file sÏ ®−îc l−u tr÷ b»ng tuú chän Save as trong thùc ®¬n File cña cöa sæ do-file editor. Tªn cña do-file cã thÓ ®−îc chØ ra ngay t¹i lÖnh doedit nh− sau: doedit (tªn do-file) TÖp do-file cã phÇn më réng l do. ë vÝ dô trªn chóng ta cã thÓ l−u tr÷ ®o¹n ch−¬ng tr×nh d−íi tªn l “ch−¬ng tr×nh 1” t¹i th− môc Vlss98 trªn æ ®Üa C. 1.2. Thùc hiÖn c¸c tÖp do-file §Ó ch¹y do-file th× t¹i cöa sæ lÖnh chóng ta gâ mét trong hai lÖnh sau: do filename [, nostop] run filename [, nostop] LÖnh run thùc hiÖn c¸c lÖnh trong do-file nh−ng kh«ng hiÓn thÞ kÕt qu¶ ra m n h×nh. Trong qu¸ tr×nh thùc hiÖn do-file, nÕu cã c©u lÖnh sai th× Stata sÏ b¸o lçi v ngõng viÖc thùc hiÖn c¸c c©u lÖnh sau ®ã. Tuy nhiªn nÕu tuú chän nostop ®−îc chØ ra th× Stata sÏ bá qua c©u lÖnh bÞ lçi v tiÕp tôc thùc hiÖn c¸c lÖnh sau c©u lÖnh lçi ®ã. VÝ dô:
- 74. 74 . do "c:vlss98chuongtrinh 1" . clear . set mem 32m (32768k) . use "C:VLSS98Hhexp98n.dta", clear . tab urban98 1:urban 98; | 0:rural 98 | Freq. Percent Cum. ------------+----------------------------------- Rural | 4269 71.16 71.16 Urban | 1730 28.84 100.00 ------------+----------------------------------- Total | 5999 100.00 . sum hhsize Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- hhsize | 5999 4.752292 1.954292 1 19 . gen new=hhsizet hhsizet not found r(111); end of do-file r(111); Víi tuú chän nostop . do "c:vlss98chuong trinh 1", nostop . clear . set mem 32m (32768k) . use "C:VLSS98Hhexp98n.dta", clear . tab urban98 1:urban 98; | 0:rural 98 | Freq. Percent Cum.
- 75. 75 ------------+----------------------------------- Rural | 426971.16 71.16 Urban | 1730 28.84 100.00 ------------+----------------------------------- Total | 5999 100.00 . sum hhsize Variable | Obs Mean Std. Dev. Min Max -------------+----------------------------------------------------- hhsize | 5999 4.752292 1.954292 1 19 . gen new=hhsizet hhsizet not found r(111); . gen new=hhsize . end of do-file Thùc hiÖn (ch¹y) b»ng lÖnh run . run "c:vlss98chuong trinh 1", nostop hhsizet not found C¸c do-file cã thÓ thùc hiÖn b»ng tuú chän Do trong thùc ®¬n File, hoÆc thùc hiÖn trùc tiÕp trong cöa sæ Do-file editor b»ng tuú chän Do hoÆc Run trong thùc ®¬n Tool. 1.3. Mét sè l−u ý khi so¹n th¶o do-file version # Khi so¹n th¶o c¸c tÖp do-file chóng ta nªn ®−a dßng lÖnh n y v o ®Çu ch−¬ng tr×nh ®Ó th«ng b¸o phiªn b¶n Stata ®−îc dïng ®Ó so¹n th¶o do-file. VÝ dô nÕu nh− chóng ta dïng Stata 7.0 ®Ó so¹n th¶o do-file th× c©u lÖnh n y sÏ ®−îc ®−a v o ®Çu ch−¬ng tr×nh nh− sau: version 7.0 clear use Hhexp98n.dta tab reg7 …. C¸c phiªn b¶n Stata kh¸c nhau sÏ cã thÓ cã sù kh¸c nhau vÒ có ph¸p hoÆc ý nghÜa cña c¸c c©u lÖnh. LÖnh version cho phÐp ch−¬ng tr×nh Stata ch¹y cã thÓ hiÓu ®óng ®−îc néi dung cña tÖp do-file ®−îc viÕt bëi c¸c phiªn b¶n kh¸c. set memory #[k|m]
- 76. 76 NÕu nh− filesè liÖu ®ßi hái bé nhí lín h¬n bé nhí m Stata ®ang sö dông th× chóng ta ph¶i thiÕt lËp bé nhí lín h¬n cho Stata b»ng lÖnh trªn. Chó ý l kh«ng nªn thiÕt lËp bé nhí lín h¬n bé nhí cña RAM m¸y tÝnh. VÝ dô: . use "C:Hhexp98n.dta", clear no room to add more observations r(901); . set mem 32m (32768k) . use "C:Hhexp98n.dta", clear set more off/on Theo chÕ ®é ngÇm ®Þnh, khi thùc hiÖn mét lÖnh nÕu nh− kÕt qu¶ cña viÖc xö lý lÖnh ®ã d i h¬n cöa sæ kÕt qu¶ (Stata Results), m n h×nh sÏ dõng l¹i v chóng ta sÏ ph¶i Ên phÝm (ch¼ng h¹n Enter hoÆc Space bar) ®Ó kÕt qu¶ tiÕp tôc ®−îc hiÓn thÞ. LÖnh set more off cho phÐp kÕt qu¶ kh«ng bÞ dõng l¹i m ®−îc hiÓn thÞ liªn tôc cho ®Õn khi thùc hiÖn xong c©u lÖnh hoÆc do-file. LÖnh set more on kh«i phôc l¹i chÕ ®é ngÇm ®Þnh. Ký tù * v /* */ Stata sÏ kh«ng thùc hiÖn c¸c c©u lÖnh ®−îc b¾t ®Çu b»ng ký tù * hoÆc n»m ë gi÷a hai nhãm ký tù /* */. C¸c ký tù n y dïng ®Ó viÕt chó thÝch trong do-file. VÝ dô: -------------------- version 7.0 set mem 32m use "C:Hhexp98n.dta", clear * Tao bien thu nhap cua ho gia dinh /* Bien nay bang Thu nhap binh quan nhan voi Quy mo ho*/ gen hhexp = rlpcex1 * hhsize #delimit ; Khi c©u lÖnh trong do-file editor qu¸ d i th× chóng ta cã thÓ dïng lÖnh n y ®Ó th«ng b¸o r»ng 1 c©u lÖnh ®−îc kÕt thóc b»ng ký tù (;). Theo chÕ ®é ngÇm ®Þnh th× c©u lÖnh ®−îc kÕt thóc khi xuèng dßng b»ng viÖc gâ phÝm Enter. §Ó kh«i phôc l¹i chÕ ®é ngÇm ®Þnh th× dïng lÖnh #delimit cr VÝ dô: ë lÖnh vÏ ®å thÞ ë ch−¬ng tr−íc: graph meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel xline (5 10 to 20) yline(2 4 to 8) connect(ll)
- 77. 77 tu¬ng ®−¬ng víi: #delimit; graph meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) b2title (Quy mo ho gia dinh) xlabel ylabel xline (5 10 to 20) yline(2 4 to 8) connect(ll) ; gen hhexp = rlpcex1 * hhsize ; …….. Sau ®ã chóng ta nªn kh«i phôc l¹i chÕ ®é ngÇm ®Þnh nÕu nh− c¸c c©u lÖnh sau ®ã cã thÓ viÕt trªn 1 dßng b»ng lÖnh: #delimit cr Chó ý: - Chóng ta cã thÓ dïng ký tù /* */ ®Ó viÕt c©u lÖnh d i nh− sau: graph meanexp meanedu ahhsize, title (Do thi chi tieu va hoc van chu ho) /* */ l1title(Chi tieu binh quan (tr dong)) l2title(So nam hoc cua chu ho) /* */ b2title (Quy mo ho gia dinh) xlabel ylabel xline (5 10 to 20) yline(2 4 to 8) connect(ll); - C¸c lÖnh # delimit v c¸ch viÕt c©u lÖnh d i sö dông ký tù /* */ chØ dïng ®−îc trong do-file chø kh«ng dïng ®−îc t¹i cöa sæ lÖnh command. 2. Local v global macros Macros l c¸c biÕn ®−îc dïng trong c¸c ch−¬ng tr×nh Stata. BiÕn macros ®−îc xem nh− 1 ®o¹n ký tù - gäi l macroname (tªn cña macros) - t−¬ng øng víi 1 d y ký tù kh¸c - ®−îc gäi l macro contents (néi dung cña macro). Cã hai lo¹i macros l local macros (macros néi bé) v global macros (macros to n bé). 2.1. Local macros NÕu chóng ta gâ: . local hogd “age hhsize rlpcex1” (DÊu nh¸y kÐp co thÓ bá qua, tøc l cã thÓ gâ: local hogd age hhsize rlpcex1) Khi ®ã th× `hogd’ sÏ ®−îc hiÓu t−¬ng ®−¬ng víi: age hhsize rlpcex1. hogd ®−îc gäi l tªn cña macros, cßn age hhsize rlpcex1 l néi dung cña macros. §Ó sö dông néi dung cña macros, chóng ta gâ tªn cña macros ë gi÷a dÊu trÝch dÉn bªn tr¸i ( ‘ ) – n»m ë phÝa trªn bªn tr¸i b n phÝm - v dÊu trÝch dÉn bªn ph¶i ( ‘ ) – n»m ë phÝa ph¶i bªn d−íi cña b n phÝm. Nh− vËy nÕu chóng ta gâ: . summarize `hogd’ th× t−¬ng ®−¬ng víi gâ:
- 78. 78 . summarize agehhsize rlpcex1 NÕu chóng ta gâ: . local tb “summarize” th× chóng ta cã thÓ thùc hiÖn lÖnh summarize age hhsize rlpcex1 b»ng c¸ch gâ: . `tb' `hogd' Variable | Obs Mean Std. Dev. Min Max -------------+------------------------------------------------------------ age | 5999 48.01284 13.7702 16 95 hhsize | 5999 4.752292 1.954292 1 19 rlpcex1 | 5999 3188.667 2692.567 357.318 45801.71 §Ó hiÓn thÞ néi dung cña local macros th× chóng ta gâ lÖnh macros list _(tªn local macros) VÝ dô: . macro list _hogd _hogd: age hhsize rlpcex1 §Ó xo¸ local macros th× chóng ta cã thÓ dung lªnh macros drop _(tªn local macros) VÝ dô: . macro drop _hogd . macro list _hogd local macro `hogd' not found r(111); 2.2. Global macros NÕu chóng ta gâ: . global diaban “reg7 province commune” (hoÆc cã thÓ bá qua dÊu ngoÆc kÐp: global diaban reg7 province commune) Khi ®ã th× $diaban t−¬ng ®−¬ng víi: reg7 province commune. diaban ®−îc gäi l tªn cña macros, cßn reg7 province commune l néi dung cña macros. §Ó sö dông ®−îc néi dung cña global macros chóng ta gâ ký hiÖu $ liÒn tr−íc tªn cña macros. Nh− vËy nÕu chóng ta gâ: . describe $diaban th× t−¬ng ®−¬ng víi gâ: . describe : reg7 province commune . describe $diaban
- 79. 79 storage display value variablename type format label variable label ------------------------------------------------------------------------------- reg7 int %8.0g Code by 7 regions province float %9.0g Province code commune float %9.0g commune code PSU-SVY commands . global mota "describe" . $mota $diaban storage display value variable name type format label variable label ------------------------------------------------------------------------------- reg7 int %8.0g Code by 7 regions province float %9.0g Province code commune float %9.0g commune code PSU-SVY commands §Ó hiÓn thÞ néi dung cña global macros th× chóng ta gâ lÖnh macros list (tªn global macros) VÝ dô: . global diaban "reg7 province commune" . macro list diaban diaban: reg7 province commune §Ó xo¸ global macros th× chóng ta cã thÓ dïng lÖnh macros drop (tªn local macros) VÝ dô: . macro drop diaban . macro list diaban global macro $diaban not found r(111); 2.3. Sù kh¸c nhau gi÷a local macros v global macros Local macros chØ tån t¹i trong 1 ch−¬ng tr×nh. Mét ch−¬ng tr×nh sÏ kh«ng hiÓu ®−îc c¸c local macros ®−îc sö dông ë c¸c ch−¬ng tr×nh kh¸c. Trong khi ®ã, mét khi ® ®−îc khai b¸o, global macros ®−îc hiÓu bëi tÊt c¶ c¸c ch−¬ng tr×nh v tån t¹i trong bé nhí cña Stata trong suèt qu¸ tr×nh ho¹t ®éng. VÝ dô: Thùc hiÖn ®o¹n ch−¬ng tr×nh khai b¸o local macros a. Sau ®ã thùc hiÖn lÖnh hiÓn thÞ néi dung local macros n y, nh−ng macros n y kh«ng tån t¹i ë ®o¹n ch−¬ng trinh kh¸c hay ë bé nhí cña Stata. . do "C:WINDOWSTEMPSTD010000.tmp" . local a "chuong trinh thong ke Stata" . end of do-file
- 80. 80 . macro list_a local macro `a' not found r(111); Trong khi ®ã ®èi víi global macros . do "C:WINDOWSTEMPSTD010000.tmp" . global b "chuong trinh thong ke Stata" . end of do-file . macro list b b: chuong trinh thong ke Stata 3. TÝch v« h−íng v ma trËn (scalar and matrix) 3.1. Ma trËn (matrix) Stata ®Þnh nghÜa ma trËn A[r, c] l mét m¶ng h×nh ch÷ nhËt gåm r h ng (row) v c cét (column). VÝ dô: NÕu ma trËn A ® ®−îc t¹o ra th× chóng ta cã thÓ xem néi dung cña ma trËn ®ã nh− sau: . matrix list A A[3,3] c1 c2 c3 r1 1 2 4 r2 3 4 7 r3 10 11 14 ë ®©y ma trËn A bao gåm 9 phÇn tö (element): 1, 2, 4, 3, 4, 7, 10, 11, 14. C¸c cét ®−îc ®Æt tªn l c1, c2, v c3, v c¸c h ng l r1, r2, v r3. PhÇn tö l giao ®iÓm cña dßng 1 v cét 2 ®−îc ký hiÖu l A[1, 2]. Trong vÝ dô n y A[1, 2] chøa gi¸ trÞ b»ng 2. 3.2. TÝch v« h−íng (scalar) TÝch v« h−íng chøa 1 phÇn tö l sè. TÝch v« h−íng ®−îc ®Þnh nghÜa b»ng lÖnh sau: scalar scalar_name = expression VÝ dô: . scalar a = 10 . scalar list a a = 10 . scalar b = a* 2 . scalar list b b = 20
- 81. 81 Trong chõng mùcn o ®ã, tÝch v« h−íng cã thÓ xem nh− mét tr−êng hîp ®Æc biÖt cña ma trËn chØ cã 1 ph©n tö (mét h ng v mét cét). 3.3. Mét sè lÖnh l m viÖc víi ma trËn ThiÓt lËp kÝch th−íc ma trËn Gia trÞ ngÇm ®Þnh cña kÝch th−íc ma trËn l tèi ®a 40 h ng v 40 cét. Chóng ta cã thÓ thay ®æi kÝch th−íc tèi ®a n y b»ng lÖnh: . set matsize 500 LÖnh n y cho phÐp c¸c ma trËn ®−îc t¹o ra cã thÓ bao gåm 500 h ng v 500 cét. T¹o ma trËn Ma trËn cã thÓ t¹o ra b»ng c¸c c©u lÖnh trùc tiÕp. VÝ dô: matrix mymat = (1,23,4) C¸c phÇn tö ®−îc ph©n biÖt bëi dÊu phÈy, cßn c¸c h ng ®−îc ph©n biÖt bëi dÊu g¹ch chÐo matrix myvec = (1 5 3 1 3) T¹o ra vÐct¬ h ng matrix mycol = (1/5/3/1/3) T¹o ra vÐct¬ cét Ma trËn còng cã thÓ ®−îc t¹o ra tõ sè liÖu b»ng lÖnh: mkmat <danh s¸ch biÕn> [®iÒu kiÖn] [ph¹m vi] [, matrix(tªn ma trËn) ] VÝ dô: . input maho quymo thunhap maho quymo thunhap 1. 101 6 1200 2. 103 5 1400 3. 105 5 3200 4. 107 9 1000 5. 109 4 2500 6. end . mkmat maho quymo thunhap, matrix(A) . matrix list A A[5,3] maho quymo thunhap r1 101 6 1200 r2 103 5 1400 r3 105 5 3200 r4 107 9 1000
- 82. 82 r5 109 42500 TÝnh to¸n ma trËn matrix D = B T¹o ra ma trËn D b»ng ma trËn B matrix C = (C+C)/2 TÝnh l¹i ma trËn C dùa trªn gi¸ trÞ cña cña nã matrix D = A*A’ T¹o ra ma trËn D b»ng tÝch ma trËn A v ma trËn chuyÓn vÞ A’ Xo¸ ma trËn Ma trËn v tÝch v« h−íng cã thÓ xo¸ khái bé nhí b»ng lÖnh: matrix drop <ma trËn> scalar drop <tÝch v« h−íng> VÝ dô: . matrix drop A . scalar drop B 4. LÖnh ®iÒu kiÖn v vßng lÆp 4.1. LÖnh if…else Có ph¸p: ®iÒu kiÖn (®iÓu kiÖn logic) { Nhãm c©u lÖnh 1 } else C©u lÖnh Stata sÏ kiÓm tra ®iÒu kiÖn logic (expression), nÕu ®iÒu kiÖn n y ®óng th× c¸c lÖnh ë Nhãm c©u lÖnh 1 sÏ ®−îc thùc hiÖn, nÕu ®iÒu kiÖn sai th× lÖnh ë ®»ng sau else sÏ ®−îc thùc hiÖn, trong tr−êng hîp else kh«ng ®−îc chØ ra th× Stata sÏ thùc hiÖn c¸c lÖnh sau lÖnh if {…}. VÝ dô: ----------------- local a=invnorm(uniform()) if `a'>=0 { display "So ngau nhien tao ra lon hon hoac bang 0" } else di "So ngau nhien tao ra nho hon 0" macro list _a Chó ý: - Sö ký hiÖu { } cho phÐp viÕt nhiÒu c©u lÖnh sau else ®iÒu kiÖn (®iÓu kiÖn) {
- 83. 83 commands 1 } else { comands2 } - C¸c lÖnh if…else cã thÓ ®−îc sö dông lång víi nhau ®iÒu kiÖn (®iÓu kiÖn) { Nhãm c©u lÖnh 1 } else ®iÒu kiÖn (®iÒu kiÖn) { …. 4.2. LÖnh while Có ph¸p: while <®iÒu kiÖn logic> { Nhãm c©u lÖnh } Stata sÏ kiÓm tra ®iÒu kiÖn logic (expression), nÕu ®iÒu kiÖn n y ®óng th× c¸c lÖnh ë “Nhãm c©u lÖnh” sÏ ®−îc thùc hiÖn, nÕu ®iÒu kiÖn sai th× c¸c lÖnh n y sÏ kh«ng ®−îc thùc hiÖn. VÝ dô: local i=1 while `i’<= 10 { if mod(`i',2) { display "`i' is odd" } else { display "`i' is even" } local i=`i’+1 } Chó ý: Vßng lÆp cã thÓ ®−îc dõng l¹i nÕu sö dông tuú chän sau ®©y ë gi÷a vßng lÆp: continue [, break] NÕu gÆp lÖnh continue, Stata sÏ bá qua c¸c lÖnh ë sau ®ã v quay l¹i lÖnh ®Çu tiªn cña vßng lÆp. NÕu c¶ tuú chän break ®−îc chØ ra th× Stata sÏ tho¸t khái vßng lÆp.
- 84. 84 VÝ dô: T×mtÝch sè chung nhá nhÊt cña 2, 3 v 5 local i=1 while `i’<= 1000 { if mod(`i',2)==0 & mod(`i',3)==0 & mod(`i',5)==0 { di "The least common multiple of 2, 3, and 5 is `i'" continue, break } } 5. Giíi thiÖu vÒ file ado T¹o ch−¬ng tr×nh Mét ®o¹n ch−¬ng tr×nh trong Stata cã thÓ ®−îc ®Þnh nghÜa b»ng lÖnh: Program define <tªn ch−¬ng tr×nh> C¸c c©u lÖnh end §o¹n ch−¬ng tr×nh n y ®−îc viÕt trong cöa sæ Do-file editor. Mét khi nã ®−îc ch¹y th× ®o¹n ch−¬ng tr×nh n y sÏ l−u tr÷ trong bé nhí cña Stata, v chØ cÇn gäi ra b»ng c¸ch gâ tªn ch−¬ng tr×nh (progname) VÝ dô: quietly program define povline display as text _col(3) "Poverty line" _col(16) "{c |}" _col(20) "Food" _col(30) "Overall" di as text _col(2) "{hline 14}{c +}{hline 26}" di as text _col(8) "Value" _col(16) "{c |}" as result _col(20) "1380" _col(33) "1920" end Sau khi chóng ta ch¹y lÖnh n y b»ng run hoÆc do, th× t¹i cöa sæ command, chóng ta gâ: . povline Poverty line | Food Overall ---------------+-------------------------- Value | 1380 1920 Chó ý: NÕu chóng ta ch¹y l¹i lÖnh program define povline, v nhËn ®−îc th«ng b¸o: povline already defined r(110); Tøc l ch−¬ng tr×nh povline ® ®−îc t¹o ra råi, ®Ó xo¸ ch−¬ng n y ®i th× chóng ta dïng lÖnh:
- 85. 85 program drop poveline hoÆcxo¸ tÊt c¶ c¸c ch−¬ng tr×nh program drop _all Ado-file C¸c ado-file t¹o ra c¸c lÖnh cña Stata. Trong Stata cã hai lo¹i lÖnh. Lo¹i thø nhÊt ®−îc viÕt trong Stata, vÝ dô nh− lÖnh summarize. Lo¹i thø hai ®−îc ®Þnh nghÜa bëi c¸c tÖp ado, vÝ dô nh− lÖnh ci. §Ó biÕt ®−îc lÖnh Stata thuéc lo¹i n o, gâ lÖnh which: . which sum built-in command: summarize . which ci C:STATAadobasecci.ado *! version 3.3.4 04sep2000 C¸c ado-file chÝnh l c¸c ch−¬ng tr×nh ®−îc ®Þnh nghÜa b»ng lÖnh program define, v l−u tr÷ víi phÇn më réng l ado. Stata sÏ t×m kiÕm c¸c ado-file ë c¸c th− môc: . sysdir STATA: C:STATA UPDATES: C:STATAadoupdates BASE: C:STATAadobase SITE: C:STATAadosite STBPLUS: c:adostbplus PERSONAL: c:adopersonal OLDPLACE: c:ado VÝ dô: Chóng ta cã thÓ l−u tr÷ lÖnh povline d−íi d¹ng ado v l−u tr÷ ë thu môc C:STATAadobase LÖnh n y sÏ ®−îc thùc hiÖn khi ta gâ povline m kh«ng cÇn chóng ta ph¶i thùc hiÖn c©u lÖnh tr−íc ë do-file. B i tËp: ViÕt lÖnh povline víi c¸c lùa chän cho c¸c n¨m 1993, 1998, v 2002. Tµi liÖu tham kh¶o H−íng dÉn sö dông trong phÇn mÒm Stata 7.0 (on-line help). (Tuú chän Contents trong thùc ®¬n Help). Phô lôc C¸c thèng kª c¬ b¶n cña mÉu tu©n theo quy luËt chuÈn Trung b×nh:
- 86. 86 n x x n 1i i∑= = Ph−¬ng sai: 1 )( 1 2 2 − − = ∑= n xx s n i i §é lÖchchuÈn: 2 ss = §é lÖch trung b×nh tuyÖt ®èi: n xx MAD n 1i i∑= − = §é lÖch: 3 n 1i 3 i s n/)xx( Skewness ∑= − = §é nhän: 4 n 1i 4 i s n/)xx( Kurtosis ∑= − =