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Re: st: Importing beta coefficients from other softwares
At 12:23 PM 5/28/2008, Maarten buis wrote:
The standard errors alone will not do, you will need the entire
variance covariance matrix. If you have that, you can do something like
this:
*------- begin example ---------------
capture program drop coefin
program define coefin, eclass
matrix b = 1, 2, 3
matrix colnames b = foo bar blup
matrix V = 3, -1, -1 \ ///
-1, 2, -1 \ ///
-1, -1, 1
matrix colnames V = foo bar blup
matrix rownames V = foo bar blup
ereturn post b V
ereturn local cmd "coefin"
end
coefin
nlcom _b[foo]/_b[bar]
This looks good for commands like test and nlcom. If, as was stated
originally, other post-estimation commands are desired, e.g. predict,
then you may need more or else not be able to do it. In particular,
if you want to predict something besides xb or stdp, you would need a
predict routine that knew how to do the necessary calculations.
It might help if we knew what Limdep can do that Stata supposedly can't.
I also wonder how hard it would be to do everything with Limdep if
for some reason you are forced to use it for the estimation. See
http://www.limdep.com/features/capabilities/post_estimation.php
Excerpts: "All model estimates are 'recoverable.' Coefficients and
asymptotic covariance matrices are retained and integrated into the
matrix algebra package. Numerical values such as log likelihoods
(individual observations and the model criterion function) and sums
of squares are recoverable and useable, by name, for example, in
testing hypotheses or computing diagnostic statistics... Program
tools are provided for manipulating results. One of the most useful
is the WALD command which is used to compute nonlinear functions and
asymptotic variances for nonlinear functions of model estimates.
Programming the derivatives for the delta method is unnecessary."
-------------------------------------------
Richard Williams, Notre Dame Dept of Sociology
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