st: problems with xi3

["E. Michael Foster" <mike4kids@gmail.com>]

Hi

I must be doing something stupid.  I'm trying to impose the normalizing 
constraint on a set of dummy variables representing a set of mutually 
exclusive categories.
A common identification constraint is to set the sum of the dummies to 
zero.  One might want to impose such a condition in an Oaxaca 
decomposition (among other reasons).  (See, for example: Gardeazabal, 
J., & Ugidos, A. (2004). More on Identification in Detailed Wage 
Decompositions. Review of Economics and Statistics, 86(4), 1034-1036.)  
As a test with the auto data, I did the following
   sort mpg
   gen mpgg=group(3)
   xi i.mpgg, prefix(D)
   for var D*: replace X=-1 if mpgg==1
   regress weight D*

I was trying to code this with xi3 but darned if I can get it right. 
   char mpgg[user] (-1 1 0 \ -1 0 1)
   xi3: regress weight u.mpgg
The two sets of estimates don't match--

Can someone explain what I'm doing wrong??

thanks--michael


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