[R-sig-ME] random effects specification

Sebastian P. Luque spluque at gmail.com
Thu Apr 3 22:45:33 CEST 2008


In the past I've used lme to fit simple mixed models to longitudinal
data (growth), but now I'm trying to learn lmer and its different syntax
to fit a more complex model.  I have a structure with subjects (id,
random factor) exposed to 4 different treatments and a continuous
response variable is measured (n).  The subjects come from 2 different
communities, so it's a nested design very much like the Oats data in the
nlme package.  The interest is in the fixed effects of community and
treatment, and their interaction, so I thought this could be modelled in
lmer with this call:

lmer(n ~ treatment + community + (1 | id/treatment), mydata)

but got this error:

Error in lmerFactorList(formula, mf, fltype) : 
  number of levels in grouping factor(s) ‘treatment:id’ is too large

Am I using the right formula here?  Thanks.


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