[R] function for "two-part" or "two-condition" models

[Richard Chandler]

Hello,

This is an (hopefully) improved question of one I posted several weeks
ago. Does anyone know of a function for fitting "two-part" models?
These models are designed to handle count data with so many zeroes
that they can't be fit well with zero-inflated Poisson models or other
'typical' GLMs. My understanding is that they work by first fitting a
binomial model to separate the zeros from the occurrences (positive
integers) before fitting a Poisson model to account for variation in
abundance. 

I have tried help.search("two-part") and many other similar guesses.

Thanks,
Richard

-- 
Richard Chandler, M.S. Candidate
Department of Natural Resources Conservation
UMass Amherst
(413)545-1237