[R] Question about lrandom effects specification in lme4

Bert Gunter gunter.berton at gene.com
Fri Dec 5 01:21:17 CET 2008


Suppose I have 3 random effects, A,B, and C. Using the older lme() function
(in nlme) it was possible (using the pdMat classes) to specify that they are
uncorrelated with identical variances. Is it possible to do this with lmer?
My understanding is that if I specify them as

lmer( y ~ ... + (A|Grp) + (B|Grp) + (C|Grp))

then they are uncorrelated but have different variances.

Motivation: I'd like to use lmer instead of lme for fitting smoothing
splines to longitudinal data.

Bert Gunter

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