[R] R-equivalent Stata command: poisson or quasipoisson?

Wil M Contreras Arbaje wil.contreras at gmail.com
Sun Sep 12 03:27:06 CEST 2010


Hello R-help,

According to a research article that covers the topic I'm analyzing,  
in Stata, a Poisson pseudo-maximum-likelihood (PPML) estimation can be  
obtained with the command

	poisson depvar_ij ln(indepvar1_ij) ln(indepvar2_ij) ...  
ln(indepvarN_ij), robust

I looked up Stata help for the command, to understand syntax and such:

	www.stata.com/help.cgi?poisson

Which simply says that the command fits a Poisson regression of depvar  
on indepvars. However, in my google-searching, I noticed that pseudo- 
maximum-likelihood estimation is sometimes called 'quasi-maximum,' and  
that R has a "quasipoisson" family that seems to allow for  
overdispersion. So, am I missing something, or should I specify  
"quasipoisson" when implementing this estimation?

Thanks a lot!

Cheers,


Wil



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