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st: constraints


From   "Kobes, Deborah" <DKobes@ui.urban.org>
To   "'statalist@hsphsun2.harvard.edu'" <statalist@hsphsun2.harvard.edu>
Subject   st: constraints
Date   Thu, 3 Oct 2002 10:28:03 -0400

I would like to use the constraints:

constraint define 1 [eq1]pnsdif =
[eq2]pnselig98_hat*[eq1]earndif/[eq2]earn98_hat;
constraint define 2 [eq1]matchdif =
[eq2]pnsmatches98_hat*[eq1]earndif/[eq2]earn98_hat

for a maximum likelihood estimator.  

When I try to do this, I get the error:

Constraints invalid:
not possible with test
r(131);

Is there any way I can set up constraints that define one coefficient in
terms of multiple other coefficients?  It works when I try to define one in
terms of only one other.

I am doing this because the ml model has two equations, each with a
different error term.  I'd like to constrain the coefficients for each part
to be equal to each other, but this has to take into consideration those
error terms.  

Thanks!
Deborah.
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