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st: predicting technical efficiency after frontier command:error message


From   "Dev Vencappa" <lexdvv@nottingham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: predicting technical efficiency after frontier command:error message
Date   Wed, 04 Aug 2004 12:28:41 +0100

>>
>>
Stata users,

 I am running the following command.
  

   reg lnrev lntoen lncap lntech lndebt
   mat X=e(b)
   local a=el(X,1,1)
  local b=el(X,1,2)
  local c=el(X,1,3)
  local d=el(X,1,4)
frontier lnrev lntoen lncap lntech lndebt, diff  uhet(lnass dumfra-dumother,noconstant)  vhet(lnass dumfra-dumother,noconstant) /*
*/from(lntoen=`a'  lncap=`b' lntech=`c' lndebt=`d')
predict CDrev1,te

I am getting my parameter estimates and everything else fine, except for the predict command which gives the following error message.

"  too many variables specified
       r(103); "

I am basically modelling heteroscedasticity in both the one-sided and two-sided error component. In contrast, when I model heteroscedasticity in either one of them, then the predict command works fine. I have read the manual and it does not say anything about possible problems with predict, te when heteroscedasticity is modelled for both error components.
   Any explanation why this is happening?

Many thanks
Dev





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