Re: st: RE: Zero Trunctated and One inflated Poisson

[Giorgio Ricchiuti <g.ricchiuti@tiscali.it>]

Thanks a lot for your reply. If I got the point are you suggesting me to 
write a program as follows?

program
version 8
args lnf mu teta
quietly replace ‘lnf’ = exp(-`teta') if $ML_y1==1
quietly replace ‘lnf’ = ln(1-exp(-`teta'))+ $ML y1*ln(`mu')- `mu' - 
lnfact($ML y1)- ln(1-exp(-`mu')) if $ML_y1>1

end
. ml model lf myoneinflated (y = x1 x2 x3) () () () ()
. ml init tau1=1 tau2=2 tau3=3 tau4=4, skip
. ml check
. ml maximize


thanks
Giorgio



Maarten Buis wrote:

> --- 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
>
>
>   
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