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st: RE: Zero Trunctated and One inflated Poisson


From   "Maarten Buis" <M.Buis@fsw.vu.nl>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Zero Trunctated and One inflated Poisson
Date   Fri, 16 Mar 2007 17:22:45 +0100

--- 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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