Message-ID: <AA561C0A-6456-403B-93D6-284E50A6AC7D@newcastle.ac.uk>
Date: 2009-12-10T16:31:21Z
From: Rob Forsyth
Subject: specifying independence of random effects?
Hello
I'm trying to specify a mixed-effect model describing "unmet NEED" (of
families with disabled children) as a function of IMPAIRMENT (i.e.
intrinsic severity of the child's condition) and AREA of residence
(factor with ~15 levels). The impairment measure is a unidimensional
variable but it needs "calibrating" for separate types of disability
(autism, cerebral palsy etc) represented by another factor, DISCAT
In lmer syntax I have
NEED ~ IMPAIRMENT | DISCAT + 1 | AREA
but I want to specify independence of random effects. I'm aware of the
pdDiag options in the nlme library but unsure how to specify the model
in lme syntax?
Thank you
Rob