Yes indeed --- remoteness of the data from the origin is a plausible
explanation.

Cheers

Andrew

On Mon, Nov 22, 2010 at 8:50 PM, S Ellison <S.Ellison@lgc.co.uk> wrote:

> Forgive the possibly numb-brained question, but is there a reason why
> the correlation between random effects coefficients in lmer should come
> out as identically 1.0 in a model of the form
>
> lmer(x ~ a + (a|b) )
>
> ?
>
> An example:
> set.seed(403)
> require(lme4)
> run <- gl(4, 15)
> conc <- rep(rep(c(0,0.1, 0.2, 0.4, 1.0), 3), 4)
> boxplot(conc~run)
> offset=0.2*as.numeric(run)
> od <- offset+conc+rnorm(60, 0, 0.2)
> plot(conc, od)
>
> (lmer1<-lmer(od~conc+(conc|run)))
> VarCorr(lmer1)
>
>
> S Ellison
> LGC
>
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