On Mon, 12 Apr 2010, David Fortunato wrote:
Hello,
I am working with zero inflated models for a current project and I am
getting wildly different results from R's zeroinfl(y ~ x, dist="negbin")
command and Stata's zinb command. Does anyone know why this may be? I find
it odd considering that zeroinfl(y ~ x, dist="poisson") gives identical to
output to Stata's zip function.
It's hard to say anything useful about this without further information
(and without having Stata available). Please provide a good example, e.g.,
the bioChemists data in "pscl" (which might also be available in Stata,
it's a standard example in the literature). Check that ZIP is in fact
identical and then check the differences between zinb and zeroinfl(). Post
the code to replicate both along with the results.
I have checked zeroinfl against some of Stata's results but only printed
in papers, manuals, etc. because I haven't access to Stata myself.
One difference might be that there are different versions of negative
binomial distributions. The one implemented in zeroinfl() is also referred
to as NB2.
Z
Thanks,
--david
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
