[R] negative predicted values in poisson glm

Ben Bolker bolker at ufl.edu
Wed Jan 18 17:21:29 CET 2006

P. Olsson <olsson1 <at> gmail.com> writes:

> Dear  R  helpers,
> running the following code of a glm model of the family poisson, gives
> predicted values < 0. Why?

  Because by default predict.glm() gives answers on the 
link (log) scale.  predict(poisson_glm,type="response")
is probably what you're looking for.  See ?predict.glm.

  Ben Bolker

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