Poisson regression

Summary

Poisson regression models a count response as Poisson distributed with a mean whose logarithm is linear in the regressors. It is the generalized linear model for Poisson responses with the canonical log link, and it is fitted by maximum likelihood. Each coefficient acts multiplicatively on the expected count, and an offset handles different exposure times or population sizes. It is the basic model for counts of events and for log-linear models of contingency tables.