Hello-
In the notes for the lm function it states " Offsets specified by offset
will not be included in predictions by predict.lm, whereas those
specified by an offset term in the formula will be." I would like to
extract fitted values in just this way from a glm model, those with the
offset and those without. I have tried doing things like this:
predict.glm(glm(Incident~Numbers, offset=logit(Numbers),
family=binomial, data=violdata))
predict.glm(glm(Incident~Numbers+offset(logit(Numbers)),
family=binomial, data=violdata))
As well as like this:
glm(Incident~Numbers, offset=logit(Numbers), family=binomial,
data=violdata)$fitted.values
glm(Incident~Numbers+offset(logit(Numbers)), family=binomial,
data=violdata)$fitted.values
But they return the same result. The first 50 lines of my data look like
this:
structure(list(Incident = c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1), Numbers = c(13L,
13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 14L, 14L, 14L, 14L, 14L,
14L, 14L, 14L, 14L, 13L, 13L, 13L, 13L, 14L, 14L, 14L, 14L, 14L,
14L, 14L, 13L, 13L, 13L, 13L, 13L, 13L, 14L, 14L, 14L, 14L, 14L,
13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L, 13L)), .Names = c("Incident",
"Numbers"), row.names = c(NA, 50L), class = "data.frame")
Any assistance gratefully recieved.
Many thanks,
Chris Beeley, Institute of Mental Health, UK
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