[R] moving from aov() to lmer()

roberto toro rto at psychology.nottingham.ac.uk
Sat Sep 13 18:17:14 CEST 2008


Hello,

I'm using this command to analyse changes in brain volume:

       mod1<-aov(Volume~Sex*Lobe*Tissue+Error(Subject/(Lobe*Tissue)),data.vslt)

I'm comparing males/females. For every subject I have 8 volume
measurements (4 different brain lobes and 2 different tissues
(grey/white matter)).

But I read that aov() results change with the order of the factors
(type I anovas). So I would like to use lmer() with type II, but I'm
struggling to find the right syntaxis...

How should I write the model I use with aov() using lmer()??

Specifying Subject as a random effect is straightforward

        mod2<-lmer(Volume~Sex*Lobe*Tissue+(1|Subject),data.vslt)

but I can't figure out the /(Lobe*Tissue) part...


Thank you very much in advance!

roberto



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