[R] Poisson Maximum Likelihood Estimation

[Paul Sweeting]

Many thanks for your suggestions on the forum (and to those that have
emailed me directly) - I'll make a start on the poisson mle approach
shortly!

Paul

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
Behalf Of Gavin Simpson
Sent: 25 January 2008 15:14
To: David Winsemius
Cc: r-help at stat.math.ethz.ch
Subject: Re: [R] Poisson Maximum Likelihood Estimation

>hits=-2.6 tests=BAYES_00
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>On Fri, 2008-01-25 at 14:21 +0000, David Winsemius wrote:
>> "Paul Sweeting" <mail at paulsweeting.co.uk> wrote in
>> news:000101c85f4e$c3d25b50$4b7711f0$@co.uk: 
><snip />
>> The most straightforward approach would be to use glm() with 
>> family="poisson", a.k.a Poisson regression.  Don't ask me why 
>> Gamma is capitalized as an R family but poisson is not, I don't know. 

>That is because there already is a gamma() for the *Gamma function*.

>>From ?glm:

>  family: a description of the error distribution and link function to
>          be used in the model. This can be a character string naming a
>          family function, a family function or the result of a call to
>          a family function.  (See 'family' for details of family
>          functions.)

>So the character string must match the *name* of the correct family
>function, hence you need to use "Gamma" even though you are not calling
>the function directly. This isn't a string to simply say which family
>you want, it has a slightly deeper meaning, hence the presumed
>inconsistency.

>I guess gamma() existed before the Gamma family function was included in
>R or S, hence it got the lowercase name "gamma".

>G

><snip />
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> Dr. Gavin Simpson             [t] +44 (0)20 7679 0522
> ECRC, UCL Geography,          [f] +44 (0)20 7679 0565
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