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
> (Phone) 410-605-7119
> (Fax) 410-605-7913 (Please call phone number above prior to faxing)
>
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--
Simon Blomberg, BSc (Hons), PhD, MAppStat.
Lecturer and Consultant Statistician
Faculty of Biological and Chemical Sciences
The University of Queensland
St. Lucia Queensland 4072
Australia
Room 320 Goddard Building (8)
T: +61 7 3365 2506
http://www.uq.edu.au/~uqsblomb
email: S.Blomberg1_at_uq.edu.au
Policies:
1. I will NOT analyse your data for you.
2. Your deadline is your problem.
The combination of some data and an aching desire for
an answer does not ensure that a reasonable answer can
be extracted from a given body of data. - John Tukey.
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