[R] negative predicted values in poisson glm

[Ben Bolker]

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