This document discusses using the NOBS option on the SET statement in SAS. It notes that NOBS returns the number of observations before any WHERE clause is applied. If the number of observations after the WHERE clause is needed, an additional DATA step is required. It also notes that the NOBS variable will not appear in the output dataset and is independent of the OBS= option. Not all SAS engines, such as XML, properly support NOBS.

1. NOBS for Noobs
David B. Horvath, CCP, MS
PhilaSUG Winter 2015 Meeting
NOBS for Noobs

2. 2
NOBS for Noobs
The Author can be contacted at:
504 Longbotham Drive, Aston PA 19014-2502, USA
Phone: 1-610-859-8826
Email: dhorvath@cobs.com
Web: http://www.cobs.com/
All trademarks and servicemarks are the
property of their respective owners.
Copyright © 2015, David B. Horvath, CCP — All Rights Reserved

3. Abstract
This mini-session will be a short discussion of the NOBS (number of
observations) option on the SET statement.
This includes one "gotcha" that I've run into with where clauses: NOBS is set
before WHERE processing. If you have a reason to know the number of
observations after the WHERE clause, another DATA step is needed.
3

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My Background
• Base SAS on Mainframe, UNIX, and PC Platforms
• SAS is primarily an ETL tool or Programming Language for me
• My background is IT – I am not a modeler
• Not my first User Group presentation – presented sessions and
seminars in Australia, France, the US, and Canada.
• Undergraduate: Computer and Information Sciences, Temple Univ.
• Graduate: Organizational Dynamics, UPenn
• Most of my career was in consulting
• Have written several books (none SAS-related)
• Adjunct Instructor covering IT topics.

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Basic NOBS
• The nobs statement is a handy way of discovering how many
observations are in your SAS Dataset:
data simple;
a = 42;
output;
run;
data _null_;
put nobs=;
stop;
set simple nobs=nobs;
run;
• Prints
NOBS=1

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Macro NOBS
• Great information if you need it!
• Is available before first row is processed
• Can be stored in macro variable for global usage:
data _null_;
call symput('ALLOBS', nobs);
stop;
set simple nobs=nobs;
run;
data _null_;
put "number of obs are &ALLOBS.";
stop;
run;
• Prints
number of obs are 1

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NOBS – the catch: where
• Processing is at the file level – before the where clause:
data _null_;
put nobs=;
stop;
set simple nobs=nobs;
run;
• And
data _null_;
put nobs=;
stop;
set simple nobs=nobs;
where a = 10;
run;
• Both print the same result:
NOBS=1

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NOBS – the catch: where
• I found out the hard way
• I had a process that rsubmitted N jobs to process the objects within an
XML file
• Each of the N jobs processed 1/Nth of the objects to spread load
• Process worked fine until the user said "Don't bother with THESE
tables".
• I figured "Oh, this is SAS, this is an easy change: 'where TABLE not
in (THESE1, THESE2, ... THESEn)'".
• The process worked fine but runtimes went up – no longer were N
processes running; the last 2 never started up.
• Solution was to add another data step in front to execute the 'where'
• Input to the rsubmit process now had the correct nobs

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NOBS – the catch: not a new variable
• Your nobs variable is special – it will not appear in the output dataset
data new;
set simple nobs=nobs;
run;
proc print data=new; run;
• Prints
Obs a
1 42
• Coding the nobs variable in a keep statement is not a fix:
data new (keep=a nobs);
WARNING: The variable nobs in the DROP, KEEP, or RENAME list
has never been referenced.
• Only solution is an equal sign (even retain does not help):
nnobs=nobs;

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NOBS – the catch: options obs=
• Is independent of options obs=;
options obs=2;
data _null_;
put nobs=;
stop;
set large nobs=nobs;
run;
• And (obs=)
data _null_;
put nobs=;
stop;
set large(obs=2) nobs=nobs;
run;
• Both print
nobs=915803

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NOBS – the catch: not every engine
• The XML Engine does not properly implement:
filename SXLEMAP "OUR_MAP_FILE.map";
filename test2 "OUR_INPUT_FILE.xml";
libname test2 xml xmlmap=SXLEMAP access=READONLY;
NOTE: Libref TEST2 was successfully assigned as follows:
Engine: XML
Physical Name: TEST2
data _null_;
put nobs=;
stop;
set test2.application nobs=nobs;
run;
• Printing
nobs=9.0071993E15
• When the file only contained 17,383,357 bytes

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Wrap Up
Questions
and
Answers
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