Design Matrix for Random effects
Hi Robert, A further problem could be that R is somewhat reluctant to fit models with interactions but without main effects. I asked this on SO quite some time ago (with nice answers from regulars on this list, Ben Bolker and Joshua Wiley): http://stackoverflow.com/q/11335923/289572 Even if you specify to exclude the main effects in presence of interaction, their parameters will be there. In your data: require(lme4) cutsim <- read.csv(file="cutsim.csv", header=T) cutsim$Species <- as.factor(cutsim$Species) cutsim$Farm <- as.factor(cutsim$Farm) # model without main effect: model2 <- lmer(Yield ~ Species + Species:Farm + (1|Animal), data=cutsim, doFit = FALSE, REML=TRUE) length(model2$fr$fixef) # 500 fixed effects parameters # model with main effect model3 <- lmer(Yield ~ Species*Farm + (1|Animal), data=cutsim, doFit = FALSE, REML=TRUE) length(model3$fr$fixef) # 500 fixed effects parameters Cheers, Henrik Am 28/05/2013 19:55, schrieb W Robert Long:
Hi Steve That's great. Thanks a lot :-) RL On 28/05/2013 18:29, Steve Walker wrote:
Hi Robert, In stable (i.e. cran) lme4, Zt can be obtained without fitting the model using this command: lmer(Reaction ~ Days + (Days|Subject), data=sleepstudy, doFit = FALSE)$FL$trms[[1]]$Zt In development (i.e. github) lme4, you can use this command: lFormula(Reaction ~ Days + (Days|Subject), data=sleepstudy)$reTrms$Zt or these two: dv <- lmer(Reaction ~ Days + (Days|Subject), data=sleepstudy, devFunOnly = TRUE) environment(dv)$pp$Zt Cheers, Steve On 2013-05-28 12:44 PM, W Robert Long wrote:
Hi all I would like to obtain the design matrix for the random effects, without running (g)lmer first. Could anyone help me do that ? For example, working with the sleepstudy dataset sm1 <- lmer(Reaction ~ Days + (Days|Subject), data=sleepstudy) sm1 at Zt is the transpose of the matrix I require, but I would like to obtain it without running lmer. Thanks Robert Long
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Dipl. Psych. Henrik Singmann PhD Student Albert-Ludwigs-Universit?t Freiburg, Germany http://www.psychologie.uni-freiburg.de/Members/singmann