Dear list,
I have been trying to apply a simple lasso regression on a 10-element
vector, just to see how this method works so as to later implement it on
larger datasets. I thus create an input vector x:
* x=rnorm(10)*
I add some noise
* noise=runif(n=10, min=-0.1, max=0.1)*
and I create a simple linear model which calculates my output vector y
* y=2*x+1+noise*
I then do
* my_data <- data.matrix(x)
model = lars(my_data, y, type = 'lasso')*
I then calculate the coefficients (type="coefficients") based on the created
*model **
preds=predict.lars(model)
for(i in 1:10){
est[i]=preds$coef[2]*x[i]
}
y.estimated=est+1+noise
*Then, I apply the same function, predict.lars, but this time with
type="fit".
* preds2=predict.lars(model,my_data)*
When I compare the *y.estimated *to *preds2$fit[,2] *I see that they are not
equal...
I provide you with the returned results:
*y.estimated:*
[2.855597 1.259374 1.673388 1.625999 0.337993 -1.672998
-1.055416 2.423278 4.092116 -1.595545]
*preds2$fit[,2]:*
[2.9120115 1.1790466 1.7452670 1.7239429 0.2893512 -1.6682459
-1.1500982 2.4364527 4.1511509 -1.6098748]
I think they should be equal...Does anyone have an explanation about that?
Thanks a lot for your time!
Eleni C.
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