Re: [R] lmer / variance-covariance matrix random effects

From: Spencer Graves <spencer.graves_at_pdf.com>
Date: Mon 31 Oct 2005 - 13:57:12 EST

          Have you received a reply to this post? I haven't seen one. I agree that VarCorr(lmer(...)) is "unhandy" if I want to do further computations with those numbers, which I often do. The following solves that problem, at least for the example in the lmer VarCorr documentation:

fm2 <- lmer(Reaction ~ Days + (1|Subject) + (0+Days|Subject), sleepstudy)) vc.lmer <- VarCorr(fm2)
str(vc.lmer) # to understand the structure

vc.lmer <- function(obj, sep=":"){

   vc <- show(VarCorr(obj))
   nR <- dim(vc)[1]
   nC <- dim(vc)[2]

   vc. <- as.numeric(vc[, nC-(1:0)])
   colNms <- dimnames(vc)[[2]][nC-(1:0)]    vcNames <- vc[,1]
   if(nC>3)for(i in 2:(nC-2))
     vcNames <- paste(vcNames, vc[,i], sep=sep)    VC <- array(vc., dim=c(nR, 2),
     dimnames=list(vcNames, colNms))
   VC
}

(tst <- vc.lmer(fm2))

                     Variance Std.Dev.
Subject:(Intercept)  627.507  25.0501
Subject:Days          35.858   5.9882
Residual:            653.589  25.5654

	  Hope this helps.
	  spencer graves

Roel de Jong wrote:

> Hello,
>
> has someone written by chance a function to extract the
> variance-covariance matrix from a lmer-object? I've noticed the VarCorr
> function, but it gives unhandy output.
>
> Regards,
> Roel de Jong
>
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-- 
Spencer Graves, PhD
Senior Development Engineer
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Received on Mon Oct 31 14:02:37 2005

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