# Predict GLM poisson with offset

I know this is probably a basic question... But I don't seem to find the answer.

I'm fitting a GLM with a Poisson family, and then tried to get a look at the predictions, however the offset does seem to be taken into consideration:

model_glm=glm(cases~rhs(data$year,2003)+lhs(data$year,2003),
offset=(log(population)), data=data, subset=28:36, family=poisson())

predict (model_glm, type="response")


I get cases not rates...

I've tried also

model_glm=glm(cases~rhs(data$year,2003)+lhs(data$year,2003)+
offset(log(population)), data=data, subset=28:36, family=poisson())


with the same results. However when I predict from GAM, using mgcv, the predictions consider the offset (I get rates).

I'm missing something?

I would appreciate any comment,

thanks

Sandra

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Please don't cross-post here and on the r-help lists ... and if you were going to post on a stackoverflow/stackexchange forum, I think SO would be better (this is a technical R question, not a stats question ...) –  Ben Bolker Apr 14 '12 at 16:23