[R-sig-ME] response variable distribution-MCMCglmm

[Walid]

Hello everyone,

I have a question regarding appropriately choosing the distribution for 
a response variable in MCMCglmm in R. My variable is a fitness trait 
calculated from the total lifetime reproductive success of the 
individual, the rate of growth of the population and individual survival 
(Following Method in Moorad(2014)).

The variable we arrived at is inflated at zero and the rest of the 
values (non-integer and non-negative) fall into an almost gaussian 
distribution (descriptively somewhat of a zero inflated Poisson 
distribution). After doing lots of research regarding extended 
distributions, the best result I found was that this variable may follow 
a Tweedie distribution, more specifically a compound Poisson-gamma 
distribution (through descriptively comparing the distributions).

The problem here is that I don't know how to include this in my MCMCglmm 
model, I do not recall if the families of distributions supported in 
MCMCglmm include Tweedie distributions. And if not, I do not know if 
there is a convenient approximation method to accommodate this.

I hope my question fits the general requirement of this list that the 
subject be related to mixed models.

Thank you in advance

-- 
Walid Mawass
Maitrise en Biologie Cellulaire et Moléculaire
Laboratoire de Génétique des Populations
Département de Chimie, Biochimie et Physique
Université du Quebec à Trois-Rivières
3351, Boul. des Forges, C.P.500
Tel. (819)-376-5011 poste 3384