Dear Dieter, I don't know whether I qualify as a "master," but here's my brief take on the subject: First, I dislike the term "least-squares means," which seems to me like nonsense. Second, what I prefer to call "effect displays" are just judiciously chosen regions of the response surface of a model, meant to clarify effects in complex models. For example, a two-way interaction is displayed by absorbing the constant and main-effect terms in the interaction (more generally, absorbing terms marginal to a particular term) and setting other terms to typical values. A table or graph of the resulting fitted values is, I would argue, easier to grasp than the coefficients, the interpretation of which can entail complicated mental arithmetic.
Regards, John ------------------------------ John Fox, Professor Department of Sociology McMaster University Hamilton, Ontario, Canada web: socserv.mcmaster.ca/jfox > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > Behalf Of Dieter Menne > Sent: June-07-08 4:36 AM > To: [EMAIL PROTECTED] > Subject: Re: [R] lsmeans > > John Fox <jfox <at> mcmaster.ca> writes: > > > I intend at some point to extend the effects package to linear and > > generalized linear mixed-effects models, probably using lmer() rather > > than lme(), but as you discovered, it doesn't handle these models now. > > > > It wouldn't be hard, however, to do the computations yourself, using > > the coefficient vector for the fixed effects and a suitably constructed > > model-matrix to compute the effects; you could also get standard errors > > by using the covariance matrix for the fixed effects. > > > > >> Douglas Bates: > https://stat.ethz.ch/pipermail/r-sig-mixed-models/2007q2/000222.html > >> > My big problem with lsmeans is > that I have never been able to understand how they should be > calculated and, more importantly, why one should want to calculate > them. In other words, what do lsmeans represent and why should I be > interested in these particular values? > >> > > Truly Confused, torn apart by the Masters > > Dieter > > ______________________________________________ > 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. ______________________________________________ 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.
