Dear Mark,
You cannot compare lm() with lme() because the likelihoods are not the same.
Use gls() instead of lm()
library(nlme)
data("sleepstudy", package = "lme4")
fm <- lm(Reaction ~ Days, sleepstudy)
fm0 <- gls(Reaction ~ Days, sleepstudy)
logLik(fm)
logLik(fm0)
fm1 <- lme(Reaction ~ Days, random= ~1|Subject, sleepstudy)
anova(fm0, fm1)
Best regards,
Thierry
----------------------------------------------------------------------------
ir. Thierry Onkelinx
Instituut voor natuur- en bosonderzoek
team Biometrie & Kwaliteitszorg
Gaverstraat 4
9500 Geraardsbergen
Belgium
Research Institute for Nature and Forest
team Biometrics & Quality Assurance
Gaverstraat 4
9500 Geraardsbergen
Belgium
tel. + 32 54/436 185
thierry.onkel...@inbo.be
www.inbo.be
To call in the statistician after the experiment is done may be no more than
asking him to perform a post-mortem examination: he may be able to say what the
experiment died of.
~ Sir Ronald Aylmer Fisher
The plural of anecdote is not data.
~ Roger Brinner
The combination of some data and an aching desire for an answer does not ensure
that a reasonable answer can be extracted from a given body of data.
~ John Tukey
> -----Oorspronkelijk bericht-----
> Van: r-help-boun...@r-project.org
> [mailto:r-help-boun...@r-project.org] Namens Mark Difford
> Verzonden: donderdag 17 maart 2011 10:55
> Aan: r-help@r-project.org
> Onderwerp: Re: [R] lmm WITHOUT random factor (lme4)
>
> On Mar 17, 2011; 11:43am Baugh wrote:
>
> >> Question: can I simply substitute a dummy var (e.g. populated by
> >> zeros) for "ID" to run the model without the random factor? when I
> >> try this R returns values that seem reasonable, but I want
> to be sure
> >> this is appropriate.
>
> If you can fit the model using lme (and it looks like you
> easily can) then another check would be:
>
> ## Compare models with and without random effects fm <-
> lm(Reaction ~ Days, sleepstudy)
> fm1 <- lme(Reaction ~ Days, random= ~1|Subject, sleepstudy)
> anova(fm1, fm) ## lme-fitted model must come first
>
> Regards, Mark.
>
> --
> View this message in context:
> http://r.789695.n4.nabble.com/lmm-WITHOUT-random-factor-lme4-t
> p3384054p3384072.html
> Sent from the R help mailing list archive at Nabble.com.
>
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