[R] GLMs: Negative Binomial family in R?

Pierre Kleiber pkleiber at honlab.nmfs.hawaii.edu
Tue Apr 5 21:05:36 CEST 2005


Check out these recent postings to the R list:

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/48429.html

http://finzi.psych.upenn.edu/R/Rhelp02a/archive/48646.html

   Cheers, Pierre


nflynn at ualberta.ca wrote:
> Greetings R Users!
> 
> I have a data set of count responses for which I have made repeated observations
> on the experimental units (stream reaches) over two air photo dates, hence the
> mixed effect.  I have been using Dr. Jim Lindsey's GLMM function found in his
> "repeated" measures package with the "poisson" family.
> 
> My problem though is that I don't think the poisson distribution is the right
> one to discribe my data which is overdispersed; the variance is greater than
> the mean.  I have read that the "negative binomial" regression models can
> account for some of the differences among observations by adding in a error
> term that independent of the the covariates.
> 
> I haven't yet come across a mixed effects model that can use the "negative
> binomial" distribution.
> 
> If any of you know of such a function - I will certainly look forward to hearing
> from you!  Additionally, if any of you have insight on zero-inflated data, and
> testing for this, I'd be interested in your comments too.  I'll post a summary
> of your responses to this list.
> 
> Best Regards,
> Nadele Flynn, M.Sc. candidate.
> University of Alberta
> 
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