response variable distribution-MCMCglmm

library(tweedie)
library(glmmTMB)
nobs <- 2000; mu <- 4; phi <- 2; p <- 1.7
set.seed(101)
  y <- rtweedie(nobs, mu=mu, phi=phi, power=p)
  twm <- glmmTMB(y ~ 1, family=tweedie())
unname( exp(fixef(twm)$cond))

exp(fixef(twm)$disp)

unname( plogis(twm$fit$par["thetaf"]) + 1)

summary(twm)

On 21Jun 2017, at 20:10, Paul Buerkner <paul.buerkner at gmail.com> wrote:

Hi Walid,

I am also not aware of any such distribution in MCMCglmm, but you may want
to try out the "hurdle_gamma" or "hurdle_lognormal" family in the brms R
package, to model positive real responses with zero-inflation.

Best,
Paul

2017-06-21 19:57 GMT+02:00 Walid <walidmawass10 at gmail.com>:

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 Mol?culaire
Laboratoire de G?n?tique des Populations
D?partement de Chimie, Biochimie et Physique
Universit? du Quebec ? Trois-Rivi?res
3351, Boul. des Forges, C.P.500
Tel. (819)-376-5011 poste 3384

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