On 2012-03-27 15:11, Ben Bolker wrote:
Lívia Dorneles Audino<livia.audino<at> gmail.com> writes:
I'm trying to make a glmm to identify the relationship between insect
species richness with fragment size, isolation and time (different years).
I already tried to analyse it using poisson distribution error, but I
always face with the following warning:
*glm.fit: fitted probabilities numerically 0 or 1 occurred *
This is probably hapenning because my dataset has a lot of zeros. So, what
error distribution should I use?
I know you haven't gotten a lot of help on r-sig-mixed-models (sorry),
but it would probably be better to post this question there. The answer
is that this is a warning, not an error, so it indicates a need for
caution but not necessarily that anything is wrong. In this case,
an internal call to glm.fit() has difficulty when it tries to fit
a subset of that data that are all-zero or all-one. It's quite possibly
OK, provided that you've looked at your results, plotted predicted values,
etc., and everything seems to make sense.
Livia:
You might also find this quite extensive recent post from Ted Harding
informative:
https://stat.ethz.ch/pipermail/r-help/2012-March/307352.html
Peter Ehlers
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