This question has been asked repeatedly (is it a FAQ?). Unfortunately other
than hard coding the constraints in your ml-program, Stata's ml-routine does
not have a capability for incorporating them. I would like to add this as a
desirable capability for Stata 8 (at least for linear constaints, but better
yet for noinlinear ones also).
Al Feiveson
-----Original Message-----
From: Kobes, Deborah [mailto:[email protected]]
Sent: Thursday, October 03, 2002 9:28 AM
To: '[email protected]'
Subject: st: constraints
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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