[R] Modelling Question

Richards, Tom richards at pci.upmc.edu
Mon Dec 18 11:29:20 CET 2000


I want to fit a model to count data where many counts are zero.  I would
like to posit that the baseline value of an immunologic marker impacts
whether or not a patient experiences any events at all, and the conditional
(on being  > 0) expectation of the remaining counts as a function of the
percent inhibition of the immunologic marker.  I guess I want to use a
logistic model for the probability of experiencing any events, and a Poisson
model for the conditional expectation.  This sounds like it should be a
familiar problem.  Before I try writing down and maximizing the likelihood
myself, can someone point me in a simpler direction?  Thanks in advance for
any help.

Tom Richards

P.S., Sorry about a potential cross-posting to S-news, but I just got a
weird "stalled, non-member posting" message from there.  I thought I was a
member of S-news, but apparently something went wrong recently for me.
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