[R-sig-ME] Crossed random effects

Kevin Wright kw.statr at gmail.com
Tue Mar 13 19:51:53 CET 2007

I am confused by some apparent contradictions about fitting crossed
random effects in software.  Consider this quote from
"To our knowledge, the only software currently available for fitting
mixed-effects models with crossed random effects is the lme4 package"

Yet, nlme and GLIMMIX appear to claim that crossed-random effects can
be fit by those respective tools:

In Mixed Effects Models in S and S-Plus:
"The crossed random-effects structure is represented in lme by a
combination of pdBlocke3d and pdIdent objects" (page 163)

"The GLIMMIX procedure, on the other hand, determines by default the
marginal log likelihood as that of an approximate linear mixed model.
This allows multiple random effects, nested and crossed random
effects, multiple cluster types, and R-side random components."  [and]
 "Example 2. Mating Experiment with Crossed Random Effects"

Are these three quotes using different definitions of "crossed random
effects"?  Have I taken the quotes out of context?  Any clarifications
would be appreciated.


K Wright

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