I am trying to calculate adjusted means according to a glm model with a
Poisson distribution using effect() in the 'effects' package. I've done
this many times before with great success, but this time I'm getting an
error. My model contains two factors and two covariates/blocks and I would
like the adjusted mean and confidence intervals for each factor separately.
The model runs without errors as does Anova() and HSD.test() on the model,
but when I try to run effect("factor", model) I get the following error:
Error in mod.matrix %*% V : non-conformable arguments

I understand that this error indicates that matrices are being created with
dimensions that can't be used in the calculations, or something to that
effect. But I don't understand enough about how the effect() function is
calculated to figure out where the problem is in my data. I checked my data
file for any NAs, missing values, etc. and can't find any problems. If
anyone has any suggestions for diagnostics or how to find the source of
this error I would greatly appreciate the help.

Thanks!

-- 
Elisha Sigmon
Ph.D. Candidate
The George Washington University
Department Of Biological Sciences
2023 G St. NW Suite 340
Washington, DC, USA 20052

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