[R-sig-ME] Problems withestimationg model in lmer

[Nicholas Lewin-Koh]

Consider the attached tumor growth data:
dat<-read.table("ListDat.txt",header=TRUE)
library(lme4)
fit<-lmer(tVol~Dose*poly(Day,2)+(Day|ID),dat)
coef(fit)
Error in coef(fit) : unable to align random and fixed effects
mcmcsamp(fit)
Error: no positive eigenvalues!
Error in t(.Call(mer_MCMCsamp, object, saveb, n, trans, verbose, deviance))
: 
  error in evaluating the argument 'x' in selecting a method for function
't'
detach(package:lme4)
library(nlme)
fit.lme<-lme(tVol~Dose*poly(Day,2),dat,random=~1+Day|ID)
coef(fit.lme)
summary(fit.lme)

works fine in lme. I think this model should be identified, is there an
estimation instability I am unaware of? My interest is in prediction not
inference, so I am not too concerned about the large number of parameters. I
am using the current R-forge version of lme4.

Thanks

Nicholas
Statistician, Genentech Inc.




 "Seek the company of those who seek the truth, and run away from those who
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