[R] glmmPQL and additive random effects?
Steve Buyske
buyske at stat.rutgers.edu
Tue Apr 22 17:02:22 CEST 2003
I'm a bit puzzled by how to write out additive random effects in
glmmPQL. In my situation, I have a factorial design on two
(categorical) random factors, A and B. At each combination, I have a
binary response, y, and two binary fixed covariates, C and D.
If everything were fixed, I would use
glm(y ~ A + B + C + D, family = binomial)
My first thought was to use
glmmPQL(y ~ A + B, random = ~ C + D, family = binomial)
but glmmPQL wants to see a grouping variable in the random term. Something like
glmmPQL(y ~ A + B, random = ~ C + D | CD, family = binomial)
where CD is a a variable combining C and D, eats up all my memory, while
glmmPQL(y ~ A + B, random = ~ 1 | CD, family = binomial)
doesn't seem like the model I want.
Perhaps this model is too hard to fit, but before I quit this
approach I want to make sure that I'm not just coding it incorrectly.
Thanks,
Steve Buyske
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