[R-sig-ME] What is the default covariance structure in the glmmPQL function (MASS package)?

[Gerda Börner]

Hello,

I sent my query to the r-project.org mailing list first where I got told to rather send it to the r-sig-mixed-models mailing list. I hope someone can help me with my question although the r-sig-mixed-models mailing list refers to issues with using lme4 rather than the glmmPQL function from the MASS package.

So here is my question:
Currently I am trying to fit a generalized linear mixed model with binary outcome using the
glmmPQL function in the MASS package.

I was wondering, which variance-covariance structure the glmmPQL function is
using by default and if it is possible to vary the variance-covariance
structure with the glmmPQL function. Unfortunately I couldn't manage to find
out myself.
If it is possible to change it, could someone tell me how to do so? I am
especially interested in a diagonal structure versus an unstructured
variance-covariance structure.

Thanks a lot in advance.

Gerda