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 ...) > 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 ______________________________________________ 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.
