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

Nicholas Lewin-Koh lewin-koh.nicholas at gene.com
Thu Feb 14 17:10:07 CET 2008

Mia culpa,
> sessionInfo()
R version 2.6.1 Patched (2007-12-16 r43718) 

LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_NUMERIC=C;LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices datasets  utils     methods   base     

other attached packages:
[1] lme4_0.999375-3   Matrix_0.999375-4 lattice_0.17-4   

loaded via a namespace (and not attached):
[1] grid_2.6.1  mgcv_1.3-29 nlme_3.1-86


-----Original Message-----
From: dmbates at gmail.com [mailto:dmbates at gmail.com] On Behalf Of Douglas
Sent: Thursday, February 14, 2008 7:20 AM
To: Nicholas Lewin-Koh
Cc: r-sig-mixed-models at r-project.org; Bert Gunter
Subject: Re: [R-sig-ME] Problems withestimationg model in lmer

2008/2/13 Nicholas Lewin-Koh <lewin-koh.nicholas at gene.com>:
> 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,
>  :
>   error in evaluating the argument 'x' in selecting a method for function
>  't'

Could you send us the output of sessionInfo() please?  A call to coef
should not generate .Call(mer_MCMCsamp, ...)

The error message about "unable to align" will go away if you use

tVol ~ Dose*(Day + Day^2) + (Day|ID)

>  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
>  have found it." - Vaclav Havel
> _______________________________________________
>  R-sig-mixed-models at r-project.org mailing list
>  https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models

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