[R] Estimating theta for negative binomial model
Prof Brian Ripley
ripley at stats.ox.ac.uk
Tue May 4 07:50:42 CEST 2010
On Mon, 3 May 2010, Tim Clark wrote:
> Dear List,
>
> I am trying to do model averaging for a negative binomial model
> using the package AICcmodavg. I need to use glm() since the package
> does not accept glm.nb() models. I can get glm() to work if I first
> run glm.nb and take theta from that model, but is there a simpler
> way to estimate theta for the glm model? The two models are:
>
> mod.nb<-glm.nb(mantas~site,data=mydata)
> mod.glm<-glm(mantas~site,data=mydata, family=negative.binomial(mod.nb$theta))
>
> How else can I get theta for the family=negative.binomial(theta=???)
library(MASS) is missing here -- do give credit where credit is due.
It contains functions
glm.convert
theta.ml
and the first does what you seem to want and the second answers the
actual question you asked.
> Thanks!
>
> Tim
>
> Tim Clark
> Department of Zoology
> University of Hawaii
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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