Hello everyone,
Apologies in advance, as this is partially a stats question and partially an R
question. I have been using a GAM to model the activity level of bats going
into and coming out from a forested edge. I had eight microphones set up in a
line transect at each of eight sites, and I am hoping to construct a model for
each of 7 species.
My count data has a reverse J-shaped skew and is overdispersed with a fair
amount of zeros, and I haven't found any transformations that will completely
normalize it (I've tried square roots and logs). Meanwhile, the variance in
call numbers varies between sites and between microphones. I wanted to use a
GAMM to incorporate varComb and varIdent, but these can only be applied on data
with a gaussian distribution.
Are there any packages I should be looking into that I don't know about that
will apply a variance structure on a negative binomial distribution? Or is
there some transformation that I should be using that will solve my normality
issues? I've been searching the R-help boards, everything in Zuur and Woods,
but I haven't found an answer yet.
Thanks very much, I am very appreciative of any help I can get on this matter.
Sincerely,
Meredith Jantzen
M.Sc. Candidate
Department of Biology
University of Western Ontario
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