[R] computation of dispersion parameter in quasi-poisson glm

Prof Brian Ripley ripley at stats.ox.ac.uk
Fri Apr 9 14:49:01 CEST 2010

On Fri, 9 Apr 2010, Sven Garbade wrote:

> Hi list,
> can anybody point me to the trick how glm is computing the dispersion
> parameter in quasi-poisson regression, eg.
> glm(...,family="quasipoisson")?

It isn't.  glm() does not need (and does not compute) the dispersion 

summary.glm will ... list it and the code is in the top few lines.
There is no 'trick': this is as described in MASS pp 186, 208 (which 
also explains some of the pitfalls).

> Thanks &regards, Sven

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

More information about the R-help mailing list