[R] nls + quasi-poisson distribution

Heather Turner Heather.Turner at warwick.ac.uk
Wed Jul 7 19:06:11 CEST 2010

Dear Suresh,

The gnm package for generalized nonlinear models might be what you want
here. This allows you to specify nonlinear models with family=quasipoisson.

For an introduction to the package see the article in R News:

If your model requires a custom "nonlin" function and you get stuck on
this, or you have any other queries about the package, I'm happy to be
contacted directly.

Best regards,


On 06/07/10 07:04, Suresh Krishna wrote:
> Hello R-helpers,
> I would like to fit a non-linear function to data (Discrete X axis,
> over-dispersed Poisson values on the Y axis).
> I found the functions gnlr in the gnlm package from Jim Lindsey: this
> can handle nonlinear regression equations for the parameters of Poisson
> and negative binomial distributions, among others. I also found the
> function nls2 in the software package accompanying the book "Statistical
> tools for nonlinear regression" by Huet et al: this can handle nonlinear
> regression with Poisson distributed Y-axis values.
> I was wondering if there was any other option: specifically, any option
> that handled nonlinear fitting with quasi-Poisson distributions (to
> handle the overdispersion).
> This is a very new area for me, and I am still trying to figure out the
> best way to do this, so I would appreciate any and all pointers.
> Thanks much, Suresh
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