[R-sig-ME] GLMM Q: Categorical fixed effects with more than 2 levels

Julie Kern juliekern27 at googlemail.com
Sat Jul 21 16:24:53 CEST 2012

I’m running a lmm (with lme) to investigate the influence of several
fixed effects on call rate. The model also includes the random terms
of group & individual identity. Several of my fixed effects are
categorical & some have more than 2 categories (up to 5). E.g. The
fixed effect habitat contains the categories ‘open’, ‘medium’ &
‘dense’. The model has shown habitat to be a significant predictor of
call rate, but I would now like to test the differences between these.
E.g. Are call rates in open, medium & dense habitats different from
each other? I am unsure how best to go about this as I still have to
take into account repeated measures from the same individuals & groups
so don’t think I can simply use a Wilcoxon signed-rank test.

Any advice would be greatly appreciated, I'm new to R & have spent a
long time searching for this on the web but am going round in ever
more confusing circles!

Thank you!


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