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st: RE: re: problem using predictnl after obtaining non-linear estimates


From   Lopa Chakraborti <lchakraborti@arec.umd.edu>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: RE: re: problem using predictnl after obtaining non-linear estimates
Date   Sun, 26 Oct 2008 11:40:59 -0400

I tried using nlcom without using any of the Xs and it seems to generate only a constant. It seems that only the point estimates of the parameters are being used and not the variance covariance matrix.
nlcom (bod1 : ($K2/($K1-$K2))*exp(-$K1)*(exp(-$K2)-exp(-$K1)))

        bod1:  (.0014539294546791/(.0009593881362685-.0014539294546791))*exp(-.0009593881
> 362685)*(exp(-.0014539294546791)-exp(-.0009593881362685))

------------------------------------------------------------------------------
downstrea~04 |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
        bod1 |   .0014508          .        .       .            .           .
------------------------------------------------------------------------------

Any help on this would be greatly appreciated.
________________________________________
From: owner-statalist@hsphsun2.harvard.edu [owner-statalist@hsphsun2.harvard.edu] On Behalf Of Kit Baum [baum@bc.edu]
Sent: Sunday, October 26, 2008 10:23 AM
To: statalist@hsphsun2.harvard.edu
Subject: st: re: problem using predictnl after obtaining non-linear estimates

<>
Lopa said

Upon inserting the @ symbol it gives me a error message:

nl wqfinalnoseasonfinal3 @ downstreamwaterqualityfoia04, nparameters(90)
@ invalid name
r(198);

Is it because I work with Stata 8.2 version?


 From -help whatsnew8to9-:

     10.  Existing command nl has a new syntax that makes estimating
nonlinear
          least-squares regressions easier.  For most models,
estimation is now as easy as
          typing the nonlinear expression.  Full programmability has
been retained for
          complex models, and the old syntax continues to work.

          nl also now supports robust (Huber/white/sandwich) and
cluster-robust SE and VCE
          estimates, including two popular adjustments that can
dramatically improve the
          small-sample performance of robust SE and VCE estimates.

          A number of new reporting and estimation options have also
been added.  See [R]
          nl.

You may be right that the syntax of -nl- is different now. However you
will have to find someone who has Stata 8.2 handy to assist with your
program. I have Stata 9 on one machine, but have long since removed
Stata 8.2.  I have no idea how the old syntax of a function evaluator
program differs (although I think it is the same in versions 9 and 10).

Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


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