Function name: zip.mle

Instead of maximising the log-likelihood via a numerical optimiser we used a Newton-Raphson algorithm which is faster. See wikipedia for the equation to be solved in the case of the zero inflated distribution. In order to avoid negative values we have used link functions, log for the \eqn{lambda} and logit for the pi as suggested by Lambert (1992). As for the zero truncated Poisson see }

Authors: Author: Michail Tsagris and Manos Papadakis