zero inflated poisson output
Brickhill, Daisy <r01db11 at ...> writes:
I am using the glmm.admb package to fit a zero-inflated poisson mixed model. What I would like to know is why when I use summary(model) the output only gives (what appears to be) the count process result. I.e. the binomial process, that deals with the zero/non zero is not shown. If you use zeroinfl() from library(pscl) it gives both 'Count model coefficients (poisson with log link)' AND 'Zero-inflation model coefficients (binomial with logit link)'. The glmm.admb output seems to give only the count model coefficients. I am using glmm.admb rather than zeroinfl() because I have a random effect. Can anyone tell me whether is a way I could extract the zero-inflation model coefficients from a glmm.admb model?
One thing to note is that the current version of glmmADMB only fits a constant model for the zero-inflation process: if you are interested in more complex zero-inflation models, you should ask here again. What version of glmmADMB are you using? (i.e. what is the output of sessionInfo() ? ) With the most recent version, when I run this example ... ## simple simulated zero-inflated Poisson example ### simulate values set.seed(101) d <- data.frame(f=factor(rep(LETTERS[1:10],each=10)),x=runif(100)) u <- rnorm(10,sd=2) d$eta <- with(d,u[f]+1+4*x) pz <- 0.3 zi <- rbinom(100,size=1,prob=pz) d$y <- ifelse(zi,0,rpois(100,lambda=exp(d$eta))) ## fit zipmodel <- glmmadmb(y~x+(1|f),data=d,family="poisson",zeroInflation=TRUE) I do get information about the zero-inflation parameter estimates ... At the moment glmmADMB is not building on r-forge, but I am trying to fix it ... Ben Bolker