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

[Ben Bolker]

Helen Ward <h.l.ward at ...> writes:

> 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?
> 
  
  Thanks for letting us know about cross-posting.

  You should be able to do this in either the MCMCglmm package or
(recent versions of) the glmmADMB package.  In MCMCglmm, use
family="ztpoisson"; in glmmADMB, use family="truncpoiss" ...

  Ben Bolker