[R] correlation/random effects when using nlme

[J-C. Marioni]

Hi,

I'm trying to use nlme to program a model where, as well as a number of 
fixed effects, I have a random effect for each subject in my model.

I would also like to include a correlation statement in my model, where the 
grouping factor for the correlation is a subset of the observations on a 
particular subject.

However, when I try and program this, R will not let me use a different 
grouping structure for the random effects and the correlation structure. I 
can't seem to solve this problem myself and so I would be grateful for any 
help!

Thanks,

John Marioni
University of Cambridge