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Re: st: xtnbreg discontinous region encountered after rescaling


From   hl <hl.statlist@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: xtnbreg discontinous region encountered after rescaling
Date   Fri, 10 Dec 2010 17:31:28 +0100

thanks maarten,

I am pretty sure the model is appropriate, I was just looking for a confirmation that such simple numerical isues can indeed make a difference in this case.

best regards,

hl






Am 10.12.2010 17:17, schrieb Maarten buis:
--- On Fri, 10/12/10, hl wrote:
I am running a series of fixed
effects negative binomial panel regressions (xtnbreg, fe) on
different dependent variables. I have encountered some
specifications that do not converge or cannot be computed
due to discontinous regions before. However, one specific
regression that worked fine suddenly returns

discontinuous region encountered
cannot compute an improvement
r(430);

after I rescaled one independent variable. I didnt change
anything substantial, just divided by factor 100 - how is
that possible?
A negative binomial model needs a lot of information to be
estimated, and a fixed effects models throws a lot of
information away (all comparisons between individuals), so
I am not surprised that you have trouble estimating your
model. In these cases numerical issues can easily matter.
It is ofcourse hard for us to determine what happend given
the information you provided, but I guess that that is what
you ran into.

Hope this helps,
Maarten

Ps. Note the remarks on anonymous question in the Statalist
FAQ section 2.1 sub 3:
<http://www.stata.com/support/faqs/res/statalist.html#tojoin>

--------------------------
Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
Germany

http://www.maartenbuis.nl
--------------------------




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