Re: [R] glm: offset

From: Simon Blomberg <s.blomberg1_at_uq.edu.au>
Date: Mon, 03 Mar 2008 13:15:48 +1000

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.
> Chief, Biostatistics and Informatics
> University of Maryland School of Medicine Division of Gerontology
> Baltimore VA Medical Center
> 10 North Greene Street
> GRECC (BT/18/GR)
> Baltimore, MD 21201-1524
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-- 
Simon Blomberg, BSc (Hons), PhD, MAppStat. 
Lecturer and Consultant Statistician 
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Received on Mon 03 Mar 2008 - 03:21:53 GMT

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