[R-sig-eco] Mixed model with zero truncated Poisson distributed data

[Mollie Brooks]

Hi Helen,
The package MCMCglmm can fit a zero truncated Poisson by specifying family="ztpoisson"
After installing and loading the package, a good place to start it the pdf brought up by
vignette("CourseNotes")
best,
Mollie

Mollie Brooks
Ph.D. Candidate
NSF IGERT Fellow
Biology Department
University of Florida
mbrooks at ufl.edu
http://people.biology.ufl.edu/mbrooks




On 11 Jan 2012, at 10:58 AM, Helen Ward wrote:

> Hello,
> 
> I am a PhD student currently trying to derive a mixed effects model.
> 
> I would like to describe the relationship between age and male 
> reproductive success in a population of greater horseshoe bats.
> 
> My data consists of three columns: MaleID, Age, NumberofPups (at that 
> age). Many of the males appear multiple times in the data set, so I 
> believe I need to derive a mixed model with MaleID as a random variable.
> 
> The data is Poisson distributed, but zero-truncated. So far I have only 
> succeeded in making a mixed model with a poisson distribution (using 
> glmmPQL in the MASS package), and a zero truncated poisson model (using 
> vglm in the VGAM package), but not a mixed model capable of handling 
> zero truncated Poisson data.
> 
> It has been suggested that I could just minus 1 from each value in the 
> NumberofPups column to make a more usual Poisson distribution, so I can 
> ignore the zero truncated bit. I have tried this and it changes the 
> results of the model, but is this an acceptable transformation?
> 
> If not, can anyone advise me on a mixed model that can handle zero 
> truncated Poisson data please?
> 
> I also intend to post this on the R-sig-mixed-models 
> <https://stat.ethz.ch/mailman/options/r-sig-mixed-models/h.l.ward%40qmul.ac.uk> 
> list, so apologies if you've seen it twice!
> 
> Many thanks,
> Helen
> 
> 
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