[R] prediction from glm

From: Hugues Santin-Janin <hsantin-janin_at_gct.org.uk>
Date: Thu 04 Aug 2005 - 21:32:47 EST

Hello r-help,  

I try to fit birds counts over years using glm. I have done (with Estate and year as factors):

Model1 <- glm(Females~Estate+Year+offset = log(area)), family = quasipoisson(link = log), na.action = "na.exclude")

After I have calculated the prediction using:

Pred1 <- predict(Model1, type = "response", na.action = "na.exclude")  

My question is: How can I obtain predictions for Females in each year that are standardized by averaging over the levels of Estate?

I have been advised to use log(area) as an offset because we are actually interested in density of birds but would appreciate any good comparisons between offset and weight.  

Thanks in advance for any help you can give.  



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