y=c(15,11,12,5,12)
lambda=50
a=1
b=1
data=list(n=length(y),y=y,lambda=lambda,a=a,b=b)
params=list("phi","N")
inits=function(){
  phi=rbeta(1,a,b)
  N=rpois(length(y),lambda)
  list(phi=phi,N=N)
}
sink("DensidadeMarginal.txt")
cat("
model{
  phi~dbeta(a,b)
  for(i in 1:n){
    N[i]~dpois(lambda)
    y[i]~dbin(phi,N[i])
  }
}",fill=T)
sink()
library(R2OpenBUGS)
fit=bugs(data,inits,params,model.file="DensidadeMarginal.txt",debug=F,n.chains=1,n.iter=100000,n.burnin=50000,n.thin=5, OpenBUGS.pgm='/home/dvd/bugs/bin/OpenBUGS')
phi=fit$sims.matrix[,"phi"]