[R] How to compute an exact Poisson model with R?

[Gabor Grothendieck]

The offset is just the log of the exposure (I assume -- I have never
used Stata)
so if you can express your model in terms of exposure
you can also express it in terms of offset.

On Fri, Aug 21, 2026 at 4:21 AM iagogv via R-help <r-help using r-project.org> wrote:
>
> Hi all,
>
> Can an exact Poisson regression be computed with R, instead of using the
> standard (glm) Poisson using maximum likelihood?
>
> I am working with a collegue in a project, and I'd like to reproduce his
> method, if not his results. He uses Stata, particularly the expoisson
> function (https://www.stata.com/help.cgi?expoisson) in order to compute
> the exact Poisson regression, relevant for small samples.
>
> expoisson fits an exact Poisson regression model, which produces more
> accurate inference in small samples than standard
> maximum-likelihood-based Poisson regression
>
> I know about exact Poisson tests
> (https://stat.ethz.ch/R-manual/R-devel/RHOME/library/stats/html/poisson.test.html),
> but it does not allow to include offset.
>
> So, is there some way to reproduce exact Poisson regression with R?
>
> Thanks!
>
> Best,
>
> --
> Iago
>         [[alternative HTML version deleted]]
>
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