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st: RE: editing e(V) matrix


From   "Ben Jann" <[email protected]>
To   <[email protected]>
Subject   st: RE: editing e(V) matrix
Date   Tue, 21 Feb 2006 15:11:13 +0100

I think -ereturn repost- cannot be used with estimates produced by -regress-because -regress- is one of the commands that does not use -ereturn post- to post its results. (Don't ask me why. StataCorp would have to comment on this) A solution to the problem is to also get the coefficients vector and -ereturn post- the transformed results. Example:

 capture program drop foo2
 program foo2, eclass
   tempname b V 
   matrix `b' = e(b)
   matrix `V' = e(V)
   matrix `V'[1,1] = 122
   ereturn post `b' `V'
   ereturn local cmd "mycmd"
 end

Note that it always advisable to define e(cmd) after posting the new results (for example, the -estimates- command will not work if e(cmd) is undefined). Depending on your needs you should also think of setting e(sample), e(N) etc.

A simple strategy to replicate everything in e() is to use Michael Blasnik -estsave- (-ssc d estsave-). Example:

 capture program drop foo2
 program foo2, eclass
   tempvar esave
   qui estsave, gen(`esave')
   qui estsave, from(`esave')
   tempname V 
   matrix `V' = e(V)
   matrix `V'[1,1] = 122
   ereturn repost V=`V'
 end 

ben

> -----Original Message-----
> From: [email protected] [mailto:owner-
> [email protected]] On Behalf Of nicolas.pistolesi
> Sent: Tuesday, February 21, 2006 2:30 PM
> To: statalist
> Subject: st: editing e(V) matrix
> 
> Dear Stata users,
> I have stata 8.2 for windows. I would like to edit the
> variance matrix e(V) after a linear regression, ereturn
> repost, seems to be the right command. I do not manage to use
> it correctly. See the log :
> 
> . capture program drop foo2;
> . program foo2, eclass;
>   1.         matrix bmat = e(V);
>   2.         matrix bmat[1,1] = 122;
>   3.         ereturn repost V = bmat;
>   4. end;
> 
> . sysuse auto;
> (1978 Automobile Data)
> 
> . quietly regress price mpg weight;
> . matrix list e(V);
> symmetric e(V)[3,3]
>                mpg      weight       _cons
>    mpg    7422.863
> weight   44.601659   .41133468
>  _cons  -292759.82  -2191.9032    12938766
> 
> . foo2;
> last estimates not found
> 
> 
> any idea why?, thank you very much for your help !
> nicolas
> 
> 
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