Question about GLMER

Dear R Help,

I believe the glmer() function in lme4 automatically fits an 
unstrucruted covariance matirx for the random effects. Is that true?

? ?If so, do I have an option to somehow ask for a
diagonal structured covariance matrix?

Hi All -

Doug, thanks for your reply. ?The context I'm looking at is a Poisson
GLMM with random (intercept,slope) for each subject. ?The
variance-covariance matrix is 2x2. ?By unstructured, I meant a 3
parameter matrix (sig1^2,sig2^2,sig12), as compared to a (reduced)
alternative diagonal structure.

Dan

-----Original Message-----
From: dmbates at gmail.com [mailto:dmbates at gmail.com] On Behalf Of Douglas
Bates
Sent: Tuesday, November 16, 2010 1:01 PM
To: Daniel Jeske
Cc: r-help at r-project.org; R-mixed models mailing list
Subject: Re: [R] Question about GLMER


I am cc:ing the R-SIG-Mixed-Models at R-project.org mailing list on this
reply as such questions are often answered more quickly on that list.

On Tue, Nov 16, 2010 at 2:00 PM, Daniel Jeske <daniel.jeske at ucr.edu>
wrote:

Dear R Help,

I believe the glmer() function in lme4 automatically fits an
unstrucruted covariance matirx for the random effects. Is that true?

The short answer is "no".

The longer answer is that you will need to be more specific about the
form of the data and the model before your question can be answered.
"unstructured" variance-covariance is SAS-speak (and an oxymoron, but I
promise not to rant about that).

So please give us a context.

? ?If so, do I have an option to somehow ask for a
diagonal structured covariance matrix?

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