[R] generating overdispersed poisson & negative binomial data

Mike Lonergan mel at mcs.st-and.ac.uk
Thu Jun 6 17:06:33 CEST 2002

I would like to try a simple parametric bootstrap, but unfortunately
(stupidly?) my models are "overdispersed" gams & glms.

I'm hoping for a function that generates overdispersed poisson or negative
binomial data with a given mean, scale (& shape parameter).

The loose definition I'm using is overdispersed poisson produces integer
values with variance=const*mean & "looks like" a poisson, & simly for
overdispersed negative binomial - I am aware that odnb is a strange thing to

Maybe the "integer-valued" bit of my definition is unnecessary, which would
mean a simple scaling would suffice, but I don't know enough to decide on
this without testing.



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