JEE Mathematics/ Lakshmikanta Satapathy/ Questions and answers part 7 involving probability distribution and determination of mean and variance of a random variable
Computer Generated Items, Within-Template Variation, and the Impact on the Pa...Quinn Lathrop
Computer Generated Items, Within-Template Variation, and the Impact on the Parameters of Response Models.
Master's thesis talk related to Lathrop, Q.N., Cheng, Y. Item Cloning Variation and the Impact on the Parameters of Response Models. Psychometrika 82, 245–263 (2017). https://doi.org/10.1007/s11336-016-9513-1
Talk at the modcov19 CNRS workshop, en France, to present our article COVID-19 pandemic control: balancing detection policy and lockdown intervention under ICU sustainability
Turin Startup Ecosystem 2024 - Ricerca sulle Startup e il Sistema dell'Innov...Quotidiano Piemontese
Turin Startup Ecosystem 2024
Una ricerca de il Club degli Investitori, in collaborazione con ToTeM Torino Tech Map e con il supporto della ESCP Business School e di Growth Capital
What price will pi network be listed on exchangesDOT TECH
The rate at which pi will be listed is practically unknown. But due to speculations surrounding it the predicted rate is tends to be from 30$ — 50$.
So if you are interested in selling your pi network coins at a high rate tho. Or you can't wait till the mainnet launch in 2026. You can easily trade your pi coins with a merchant.
A merchant is someone who buys pi coins from miners and resell them to Investors looking forward to hold massive quantities till mainnet launch.
I will leave the what's app number of my personal pi vendor to trade with.
+12349014282
Seminar: Gender Board Diversity through Ownership NetworksGRAPE
Seminar on gender diversity spillovers through ownership networks at FAME|GRAPE. Presenting novel research. Studies in economics and management using econometrics methods.
Abhay Bhutada Leads Poonawalla Fincorp To Record Low NPA And Unprecedented Gr...Vighnesh Shashtri
Under the leadership of Abhay Bhutada, Poonawalla Fincorp has achieved record-low Non-Performing Assets (NPA) and witnessed unprecedented growth. Bhutada's strategic vision and effective management have significantly enhanced the company's financial health, showcasing a robust performance in the financial sector. This achievement underscores the company's resilience and ability to thrive in a competitive market, setting a new benchmark for operational excellence in the industry.
how to swap pi coins to foreign currency withdrawable.DOT TECH
As of my last update, Pi is still in the testing phase and is not tradable on any exchanges.
However, Pi Network has announced plans to launch its Testnet and Mainnet in the future, which may include listing Pi on exchanges.
The current method for selling pi coins involves exchanging them with a pi vendor who purchases pi coins for investment reasons.
If you want to sell your pi coins, reach out to a pi vendor and sell them to anyone looking to sell pi coins from any country around the globe.
Below is the what'sapp information for my personal pi vendor.
+12349014282
Yes of course, you can easily start mining pi network coin today and sell to legit pi vendors in the United States.
Here the what'sapp contact of my personal vendor.
+12349014282
#pi network #pi coins #legit #passive income
#US
STREETONOMICS: Exploring the Uncharted Territories of Informal Markets throug...sameer shah
Delve into the world of STREETONOMICS, where a team of 7 enthusiasts embarks on a journey to understand unorganized markets. By engaging with a coffee street vendor and crafting questionnaires, this project uncovers valuable insights into consumer behavior and market dynamics in informal settings."
What website can I sell pi coins securely.DOT TECH
Currently there are no website or exchange that allow buying or selling of pi coins..
But you can still easily sell pi coins, by reselling it to exchanges/crypto whales interested in holding thousands of pi coins before the mainnet launch.
Who is a pi merchant?
A pi merchant is someone who buys pi coins from miners and resell to these crypto whales and holders of pi..
This is because pi network is not doing any pre-sale. The only way exchanges can get pi is by buying from miners and pi merchants stands in between the miners and the exchanges.
How can I sell my pi coins?
Selling pi coins is really easy, but first you need to migrate to mainnet wallet before you can do that. I will leave the what'sapp contact of my personal pi merchant to trade with.
+12349014282
when will pi network coin be available on crypto exchange.DOT TECH
There is no set date for when Pi coins will enter the market.
However, the developers are working hard to get them released as soon as possible.
Once they are available, users will be able to exchange other cryptocurrencies for Pi coins on designated exchanges.
But for now the only way to sell your pi coins is through verified pi vendor.
Here is the what'sapp contact of my personal pi vendor
+12349014282
5 Tips for Creating Standard Financial ReportsEasyReports
Well-crafted financial reports serve as vital tools for decision-making and transparency within an organization. By following the undermentioned tips, you can create standardized financial reports that effectively communicate your company's financial health and performance to stakeholders.
where can I find a legit pi merchant onlineDOT TECH
Yes. This is very easy what you need is a recommendation from someone who has successfully traded pi coins before with a merchant.
Who is a pi merchant?
A pi merchant is someone who buys pi network coins and resell them to Investors looking forward to hold thousands of pi coins before the open mainnet.
I will leave the what'sapp contact of my personal pi merchant to trade with
+12349014282
1. Arthur Charpentier, SIDE Summer School, July 2019
# 5 Classification & Boosting
Arthur Charpentier (Universit´e du Qu´ebec `a Montr´eal)
Machine Learning & Econometrics
SIDE Summer School - July 2019
@freakonometrics freakonometrics freakonometrics.hypotheses.org 1
2. Arthur Charpentier, SIDE Summer School, July 2019
Starting Point: Classification Tree
1 library(rpart)
2 cart = rpart(PRONO˜.,data=
myocarde)
3 library(rpart.plot)
4 prp(cart ,type=2, extra =1)
A (binary) split is based on one specific variable âĂŞ say xj âĂŞ and a cutoff,
say s. Then, there are two options:
• either xi,j ≤ s, then observation i goes on the left, in IL
• or xi,j > s, then observation i goes on the right, in IR
Thus, I = IL ∪ IR.
@freakonometrics freakonometrics freakonometrics.hypotheses.org 2
3. Arthur Charpentier, SIDE Summer School, July 2019
Classification : Classification Trees
Gini for node I is defined as
G(I) = −
y∈{0,1}
py(1 − py)
where py is the proportion of individuals in the leaf of type y,
G(I) = −
y∈{0,1}
ny,I
nI
1 −
ny,I
nI
1 gini = function(y,classe){
2 T. = table(y,classe)
3 nx = apply(T,2,sum)
4 n. = sum(T)
5 pxy = T/matrix(rep(nx ,each =2) ,nrow =2)
6 omega = matrix(rep(nx ,each =2) ,nrow =2)/n
7 g. = -sum(omega*pxy*(1-pxy))
8 return(g)}
@freakonometrics freakonometrics freakonometrics.hypotheses.org 3
4. Arthur Charpentier, SIDE Summer School, July 2019
Classification : Classification Trees
1 -2*mean(myocarde$PRONO)*(1-mean(myocarde$PRONO))
2 [1] -0.4832375
3 gini(y=myocarde$PRONO ,classe=myocarde$PRONO <Inf)
4 [1] -0.4832375
5 gini(y=myocarde$PRONO ,classe=myocarde [ ,1] <=100)
6 [1] -0.4640415
@freakonometrics freakonometrics freakonometrics.hypotheses.org 4
5. Arthur Charpentier, SIDE Summer School, July 2019
Classification : Classification Trees
if we split, define index
G(IL, IR) = −
x∈{L,R}
nx
nIx
nI
y∈{0,1}
ny,Ix
nIx
1 −
ny,Ix
nIx
the entropic measure is
E(I) = −
y∈{0,1}
ny,I
nI
log
ny,I
nI
1 entropy = function(y,classe){
2 T = table(y,classe)
3 nx = apply(T,2,sum)
4 pxy = T/matrix(rep(nx ,each =2) ,nrow =2)
5 omega = matrix(rep(nx ,each =2) ,nrow =2)/sum(T)
6 g = sum(omega*pxy*log(pxy))
7 return(g)}
@freakonometrics freakonometrics freakonometrics.hypotheses.org 5
9. Arthur Charpentier, SIDE Summer School, July 2019
Boosting & Adaboost
Classification problem, yi ∈ {•, •}, consider a model at stage
k − 1,
if mk−1(xi) = yi, increase the weight given to observation i
Boosting : weak learner
A weak model is a model slightly better than a pure
random one (head/tails)
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@freakonometrics freakonometrics freakonometrics.hypotheses.org 9
10. Arthur Charpentier, SIDE Summer School, July 2019
Boosting & Adaboost
Classification problem, yi ∈ {•, •}, consider a model at stage
k − 1,
if mk−1(xi) = yi, increase the weight given to observation i
Boosting : weak learner
A weak model is a model slightly better than a pure
random one (head/tails)
q
q
q
q
q
q
q
q
q
q
0.0 0.2 0.4 0.6 0.8 1.0
0.00.20.40.60.81.0
0.5
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@freakonometrics freakonometrics freakonometrics.hypotheses.org 10
11. Arthur Charpentier, SIDE Summer School, July 2019
Boosting & Adaboost
Adaboost Algorithm
1. Set weights ωi = 1/n, i = 1, · · · , n
2 . For k = 1, · · ·
(i) fit model on (yi, xi) with weights ωi, get hk(x)
(ii) compute the error rate εk =
n
i=1
˜ωi1yi=hk(xi)
(iii) compute αk = log
1 − εk
εk
(iv) reevaluate the weights ωi = ωi · eαk1yi=hk(xi)
3. The final model is hκ(x) =
κ
k≥1
αkhk(x)
The error rate should not be too small (εk ≤ 50%) to insure αk > 0
@freakonometrics freakonometrics freakonometrics.hypotheses.org 11
12. Arthur Charpentier, SIDE Summer School, July 2019
Boosting & Adaboost
The general problem in machine learning is to find m (·) = argmin
m∈M
E (Y, g(X)
Use loss (y, g(x)) = 1y=g(x.
Empirical version is mn(·) = argmin
m∈M
1
n
n
i=1
(yi, g(xi) = argmin
m∈M
1
n
n
i=1
1yi=g(xi)
Complicated problem : use a convex version of the loss function
(y, g(x) = exp[−y · g(x)]
From Hastie et al. (2009), with the adaboost algorithm,
hκ(·) = hκ−1(·) + ακhκ(x) = hκ−1(·) + 2β H (·)
where (β , H (·)) = argmin
(β,H)∈(R,M)
n
i=1
exp − yi · (hκ−1(xi) + βH(xi)
@freakonometrics freakonometrics freakonometrics.hypotheses.org 12
21. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting
Newton-Raphson to minimize a strictly convex function g : R → R
At minimum, g (x ) = 0, so consider first order approximation
g (x + h) ≈ g (x) + h · g (x)
Consider sequence xk = xk−1 − αg (xk−1) where α = [g (xk−1)]−1
One can consider a functional version of that technique, ∀i = 1, · · · , n,
gk(xi) = gk−1(xi) − α
∂ (yi, g(xi))
∂g(xi) g(xi)=gk−1(xi)
This provides a sequence of function gk at points xi.
To get values at any point x use regression i’s on xi’s,
εi = −
∂ (yi, g))
∂g g=gk−1(xi)
If α = 1 and (y, g) = exp[−yg], we have (almost) adaboost
@freakonometrics freakonometrics freakonometrics.hypotheses.org 21
22. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting
Gradient Boosting Algorithm
1. Start with a constant model, h0(x) = argmin
c∈R
1
n
n
i=1
(yi, c) and a regu-
larization parameter α ∈ (0, 1)
2 . For k = 1, · · ·
(i) compute εi = −
∂ (yi, g))
∂g g=gk−1(xi)
(ii) fit the (weak) model on sample (εi, xi) and let Hk denote the mode
(iii) update the model hk(·) = hk−1(·) + αHk(·)
3. The final model is hκ(x)
The choice of α is (somehow) not important : use α ∼ 10%
@freakonometrics freakonometrics freakonometrics.hypotheses.org 22
23. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting
The logiboost model is obtained when y ∈ {0, 1} and loss function is
(y, m) = log[1 + exp(−2(2y − 1)m)]
Boosting (learning from the mistakes)
Sequential Learning
mk(·) = mk−1(·) + α · argmin
h∈H
n
i=1
yi − mk−1(xi)
εi
, h(xi)
Hence, learning is sequential, as opposed to bagging...
@freakonometrics freakonometrics freakonometrics.hypotheses.org 23
24. Arthur Charpentier, SIDE Summer School, July 2019
Bagging
Gradient Boosting Algorithm
1. For k = 1, · · ·
(i) draw a bootstrap sample from (yi, xi)’s
(ii) estimate a model mk on that sample
2. The final model is m (·) =
1
κ
κ
i=1
mk(·)
To illustrate, suppose that m is some parametric model mθ.
mk = mθk
, obtained some sample Sk = {(yi, xi), i ∈ Ik}.
Let σ2
(x) = Var[mθ
(x)] and ρ(x) = Corr[mθ1
(x), mθ2
(x)] obtained on two
ramdom boostrap samples
Var[m (x)] = ρ(x)σ2
(x) +
1 − ρ(x)
κ
σ2
(x)
@freakonometrics freakonometrics freakonometrics.hypotheses.org 24
25. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting & Computational Issues
We have used (y, g(x) = exp[−y · m(x)] instead of 1y=m(x.
Misclassification error is (upper) bounded by the exponential loss
1
n
n
i=1
1yi·m(xi
≤
1
n
n
i=1
exp[−yi · m(xi]
Here m(x) is a linear combination of weak classifier, m(x) =
κ
j=1
αjhj(x).
Let M = [Mi,j] where Mi,j = yi · hj(xi) ∈ {−1, +1}, i.e. Mi,j = 1 whenever
(weak) classifier j correctly classifies individual i.
yi · m(xi) =
κ
j=1
αjyihj(xi) = Mα i
thus, R(α) =
1
n
n
i=1
exp[−yi · m(xi)] =
1
n
n
i=1
exp − (Mα)i
@freakonometrics freakonometrics freakonometrics.hypotheses.org 25
26. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting & Computational Issues
One can use coordinate descent, in direction j in which the directional derivative
is the steepest,
j ∈ argmin −
∂R(α + aej)
∂a a=0
where the objective can be written
−
∂
∂a
1
n
n
i=1
exp − (Mα)i − a(Mej)i
a=0
=
1
n
n
i=1
Mij exp − (Mα)i
Then
j ∈ argmin (d M)j where di =
exp[−(Mα)i]
i exp[−(Mα)i]
@freakonometrics freakonometrics freakonometrics.hypotheses.org 26
27. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting & Computational Issues
Then do a line-search to see how far we should go. The derivative is null if
−
∂R(α + aej)
∂a
= 0 i.e. a =
1
2
log
d+
=
1
2
log
1 − d−
d−
where d− =
i:Mi,j =−1
di and d+ =
i:Mi,j =+1
di.
Coordinate Descent Algorithm
1. di = 1/n for i = 1, · · · , n and α = 0
2 . For k = 1, · · ·
(i) find optimal direction j ∈ argmin (d M)j
(ii) compute − =
i:Mi,j =−1
di and ak =
1
2
log
1 − d−
d−
(iii) set α = α + akej and di =
exp[−(Mα)i]
i exp[−(Mα)i]
@freakonometrics freakonometrics freakonometrics.hypotheses.org 27
28. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting & Computational Issues
very close to Adaboost : αj is the sum of ak where direction j was considered,
αj =
κ
k=1
ak1j (k)=j
Thus
m (x) =
κ
k=1
αjhj(x) =
κ
k=1
akhj (k)(x)
With Adaboost, we go in the same direction, with the same intensity : Adaboost
is equivalent to minimizing the exponential loss by coordinate descent.
Thus, we seek m (·) = argmin E(Y,X)∼F
exp (−Y · m(X))
which is minimized at m (x) =
1
2
log
P[Y = +1|X = x]
P[Y = −1|X = x]
(very close to the logistic regression)
@freakonometrics freakonometrics freakonometrics.hypotheses.org 28
29. Arthur Charpentier, SIDE Summer School, July 2019
Gradient Boosting & Computational Issues
Several packages can be used with R, such as adabag::boosting
1 library(adabag)
2 library(caret)
3 indexes= createDataPartition (myocarde$PRONO , p=.70 , list = FALSE)
4 train = myocarde[indexes , ]
5 test = myocarde[-indexes , ]
6 model = boosting(PRONO˜., data=train , boos=TRUE , mfinal =50)
7 pred = predict(model , test)
8 print(pred$confusion)
9 Observed Class
10 Predicted Class DECES SURVIE
11 DECES 5 0
12 SURVIE 3 12
or use cross-validation
1 cvmodel = boosting.cv(PRONO˜., data=myocarde , boos=TRUE , mfinal =10, v
=5)
@freakonometrics freakonometrics freakonometrics.hypotheses.org 29