On Mar 27, 2013, at 7:00 PM, Ben Bolker wrote: > Michael Grant <michael.grant <at> colorado.edu> writes: > >> >> >> Dear Help: > >> I am trying to follow Professor Bates' recommendation, quoted by >> Professor Crawley in The R Book, p629, to determine whether I should >> model data using the 'plain old' lm function or the mixed model >> function lmer by using the syntax anova(lmModel,lmerModel). >> Apparently I've not understood the recommendation or the proper >> likelihood ratio test in question (or both) for I get this error >> message: Error: $ operator not defined for this S4 class. > > I don't have the R Book handy (some more context would be extremely > useful! I would think it would count as "fair use" to quote the > passage you're referring to ...)
This is the quoted Rhelp entry: http://tolstoy.newcastle.edu.au/R/help/05/01/10006.html (I'm unable to determine whether it applies to the question at hand.) > >> Would someone be kind enough to point out my blunder? > > You should probably repost this to the r-sig-mixed-mod...@r-project.org > mailing list. > > My short answer would be: (1) I don't think you can actually > use anova() to compare likelihoods between lm() and lme()/lmer() > fits in the way that you want: *maybe* for lme() [don't recall], > but almost certainly not for lmer(). See http://glmm.wikidot.com/faq > for methods for testing significance/inclusion of random factors > (short answer: you should *generally* try to make the decision > whether to include random factors or not on _a priori_ grounds, > not on the basis of statistical tests ...) > > Ben Bolker > -- David Winsemius Alameda, CA, USA ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.