Re: [R] lme model: Error in MEEM

From: Douglas Bates <dmbates_at_gmail.com>
Date: Thu 18 Aug 2005 - 23:29:52 EST

On 8/18/05, Christoph Lehmann <christoph.lehmann@gmx.ch> wrote:
> Hi,
> We have data of two groups of subjects: 32 elderly, 14 young adults. for
> each subject we have 15 observations, each observation consisting of a
> reaction-time measure (RT) and an activation maesure (betadlpcv).
> since we want to analyze the influence of (age-)group and RT on the
> activation, we call:
>
> lme(betadlpcv ~ RT*group, data=our.data, random=~ RT |subject)
>
> this yields:
> Error in MEEM(object, conLin, control$niterEM) :
> Singularity in backsolve at level 0, block 1
> In addition: Warning message:
> Fewer observations than random effects in all level 1 groups in:
> lme.formula(betadlpcv ~ RT * group, data = patrizia.data, random = ~RT |
>
> what's the problem here?

It seems that you only have one observation per subject and you are trying to estimate a model with two random effects per subject plus the per-observation noise term. These terms are completely confounded.
>
> thanks for your kind help
> christoph
>
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R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Aug 18 23:35:25 2005

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