[R] lmer and glmmPQL

From: Cox, Stephen <stephen.cox_at_ttu.edu>
Date: Tue 06 Dec 2005 - 10:03:16 EST


I have been looking into both of these approaches to conducting a GLMM, and want to make sure I understand model specification in each. In particular - after looking at Bates' Rnews article and searching through the help archives, I am unclear on the specification of nested factors in lmer. Do the following statements specify the same mode within each approach?

m1 = glmmPQL(RICH ~ ZONE, family = poisson, data, random = ~ YEAR | SITE / QUADRAT)
m2 = lmer(RICH ~ ZONE +(YEAR|SITE)+ (YEAR|QUADRAT), family = poisson, data)

As a follow up - what would be the most appropriate model formula (using glmmPQL syntax) to specify both a nested facor and repeated observations? Specifically, I am dealing with experimental data with three factors. ZONE is a fixed effect. Three sites (SITE) are nested within each ZONE. Multiple quadrats within each SITE are measured across multiple years. I want to represent the nesting of SITE within ZONE and allow for repeated observations within each QUADRAT over time (the YEAR | QUADRAT random effect). -- I am assuming that glmmPQL is the best option at this point because of recent discussion on Rhelp about issues associated with the Matrix package used in lmer (i.e., the anova results do not seem to match parameter tests).

Any information would be very much appreciated!

Regards

Stephen



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