On Apr 14, 2012, at 6:47 PM, smfa wrote:
Hi,
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).
The beta coefficients are the log-rate-estimates when you use
log(population) as the offset.
I'm missing something?
You are most definitely missing the part where you include 'data'.
--
David Winsemius, MD
West Hartford, CT
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