glm: offset
Yes, use the log. I've had the same problem in the past, too. Try it on a toy example to confirm it for yourself. Cheers, Simon.
On Sun, 2008-03-02 at 22:01 -0500, John Sorkin wrote:
R 2.6.0
Windows XP
A question about running a generalized linear model.
I am running a glm with
(1) a poisson distribution and a log link:
family=poisson(link = "log")
and an offset.
I would like to know if I should express the offset as the log of the offset value, i.e.
offset=log(NumUniqPt)
or as:
offset=NumUniqPt
I suspect I need to use the log, bu t I can't find any discussion of this in MASS 1994 or on the man page for glm.
Thanks
John
John Sorkin M.D., Ph.D.
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