--- On Tue, 10/3/09, jjc.li@utoronto.ca <jjc.li@utoronto.ca> wrote:
I have to regress the translog cost function with
parametric restrictions. One of the restrictions is
a11= -d11^2+a1-a1^2
a12= -d11d21-a2a1
.................
a33= -d31^2-d32^2-d33^2+a3-a3^2
a11 to a33 are all parameters appeared in the cost function
and other constraints, but d11 to d33 are all unknown
numbers. So how to define the constrain above in stata?
I see to difficulties here (all solvable, but not easily): First, the
constraints are non-linear (they include a square term). Second,
they contain numbers that apperently need to be estimated (the d-s).
Both problems rule out using the -constraint- command, which would
be the easy way of including constraints. What might be possible is
to rewrite this model as a nonlinear least squares problem, in which
case you can use -nl- to estimate this model. If that is not
possible then you can define your own likelihood function which has
these constraints hard coded in. The way to do that in Stata is to
use the -ml- command. If you choose to go that way then you will
probably need access to this book
http://www.stata-press.com/books/ml.html
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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