On Wed, 29 Aug 2001, Christian Hennig wrote:
> Dear list,
>
> the following should fit the model
> log(PEPC.Wert)=fKTemp+fHerk+interaction(fKTemp,fHerk)+fMub+error,
> where fKTemp, fHerk are fixed effect factors and fMub is a random effects
> factor nested in fHerk (values are different fopr different values of
> fHerk).
>
> > logpepcr1 <- lme(log(PEPC.Wert) ~ fKTemp*fHerk, random= ~ 1 | fMub,
na.action=na.omit)
>
> The following should be without the random factor:
>
> > logpepcr0 <- lme(log(PEPC.Wert) ~ fKTemp*fHerk,na.action=na.omit)
> Error in getGroups.data.frame(dataMix, groups) :
> Invalid formula for groups
>
> OK, I try with lm:
>
> > logpepcr0 <- lm(log(PEPC.Wert) ~ fKTemp*fHerk,na.action=na.omit)
>
> ...works.
>
> Is the following correct for testing the significance of the
> random factor?
>
> > anova.lme(logpepcr0,logpepcr1)
> Model df AIC BIC logLik Test L.Ratio p-value
> logpepcr0 1 10 3977.354 4030.318 -1978.677
> logpepcr1 2 11 3885.392 3943.653 -1931.696 1 vs 2 93.96144 <.0001
No. You need to fit the lme model by maximum likelihood, not the default
REML, to be comparable with the lm fit.
> Where can I get an estimator for the variance of the random factor fMub?
The standard error is in the summary() output.
> Is there a way to specify an interaction between fMub and fKTemp?
>
> And why does this happen?
>
> > plot(logpepcr1)
> Error in do.call(plotFun, as.list(args)) :
> couldn't find function "xyplot"
That's a legacy of the S origins: xyplot is in package lattice in the
Devel section on CRAN (needs grid too) and I don't know if it
yet suffices for plot.lme.
> (plot(logpepcr0) works; I use R 1.3.0 on Solaris.)
That's using plot.lm.
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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