--- Giorgio Ricchiuti wrote:
> I have been modelling the number of affiliates that the firm i has in
> the country j. My data are zero-truncated but unfortunately are even
> one-inflated (75% of cases). I did not find any possibility to analyse
> this mix-model in STATA 9.0 (neither using for example zip or ztp). I
> worked out the maximum likelihood, and I changed the adofile of zip as
> follows:
<snip>
> Of course I also changed gradient and hessian but, unfortunately, I am
> not a developer, hence I did some mistake.
>
> Does anyone help me, explaining either how to change the maximum
> likelihood correctly or developing the model directly in Stata?
Most user written ml commands use lf instead of d2 because lf is much
easier to program. You can use my ``zero inflated logit'' program I sent
to the statalist this morning as a template:
http://www.stata.com/statalist/archive/2007-03/msg00633.html .
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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