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st: RE: constraints

From   "FEIVESON, ALAN H. (AL) (JSC-SD) (NASA)" <>
To   "''" <>
Subject   st: RE: constraints
Date   Thu, 3 Oct 2002 10:06:51 -0500

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 []
Sent: Thursday, October 03, 2002 9:28 AM
To: ''
Subject: st: constraints

I would like to use the constraints:

constraint define 1 [eq1]pnsdif =
constraint define 2 [eq1]matchdif =

for a maximum likelihood estimator.  

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

Constraints invalid:
not possible with test

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.  

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