[R-sig-ME] Measure of influence for lmer models

[Jenn Barrett]

Hi everyone,

My colleague and I recently fit a linear mixed effects model with lmer(), and after looking at the results, my supervisor is interested in having me examine the influence of individual observations (he suspects that there may be a couple high leverage points); however, I'm at a loss on how to do this with a "mer" object. Is there a function/method for computing Cook's distance, leverage plots or some other measure of influence for "mer" objects? I've searched the forum, but have only come across unanswered questions.

Thanks in advance.  

Jenn