Re: st: RE: How to skip logit when there is no variation in the dependentvariable

[Thomas de Hoop <T.deHoop@maw.ru.nl>]

Thank you very much Maarten!

Thomas

Maarten Buis wrote:
> if pseudo Stata code (assuming that drought`i' is missing for other countries than country `i'):
>
> forval i=1/214 {
>     count if drought`i'==0
>     if r(N) > 0 logit drought`i' variable1 variable 2 etc. 
> }
>
> 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/
> -----------------------------------------
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Thomas de Hoop
> Sent: maandag 19 maart 2007 11:11
> To: statalist@hsphsun2.harvard.edu
> Subject: st: How to skip logit when there is no variation in the dependent variable
>
> Dear Statalist users,
>
> I have created dummy variables for 214 countries. For each of these
> countries I want to estimate several logit models to estimate chances of
> certain situations to occur,  and create chance variables from the
> prediction of these models. I estimate these chances using data from the
> past. I have data of these situation For this I created loops with the
> foreach and forvalue commands from stata. The problem is that in some
> countries a certain situation never occurred. For these situations there
> are only 0 value observations. Of course logistic regression is not
> possible in these kind of situations. For this reason I would like to
> skip these equations in the loop.
> For this reason I counted the number of times a situation did occur in
> the past and created a variable.
>
> I tried to skip the equation as follows:
>
> forval i=1/214 {
> logit drought`i' variable1 variable 2 etc. if  droughtcount`i'>0
> }
>
> i= the country number
> variable1 variable2 etc are the explanatory variables.
>
> drought`i'=the situation in a certain country
> droughtcount`i'=the number of times a situation did occur in the past.
>
> For country 3 this results in the following error:
> no observations
> r(2000);
>
> How can I prevent this error?
>
> Best regards,
>
> Thomas de Hoop
>
>
>
>
>
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