Dear all, I have a mixed Poisson regression model . my function is: ## P(N=k)=[(a+2)/a ][(lambda^k)]*[((a+2/a+1)+lambda)^(-k-1)-(a+2+lambda)^(-k-1)]; lambda=a0+a1*x1+a2*x2 This is same as a Poisson-inverse gaussian or Poisson-lognormal regression.I want to estimate the parameters by fitting this model on my data and also I need loglike value. Since some of the explanatory variables (x1,x2,...) may be nominal or ordinal; which package in R can be used? I am looking for any answer. with the best wishes Zamani.H [[alternative HTML version deleted]]