Unbalanced ANOVA in R?

The lme() function doesn't need aov(). So you would type:

lme(DELAY ~ DOSE + TRIALS,data=epinuneq)

however see ?lme o some book about mixed models: you need to specify the
random part and "clustering" variable (e.g. id-subject in a repeated
measurement design). Something like

lme(DELAY ~ DOSE + TRIALS, random=~1|your_cluster_variable, data=epinuneq)

best,
vito

After all, I don't think that simple "unbalanced ANOVA" and mixed models are
the same!


----- Original Message -----
From: "Fredrik Karlsson" <fredrik.karlsson at ling.umu.se>
To: "r-help-request Mailing List" <r-help at r-project.org>
Sent: Friday, March 08, 2002 6:56 AM
Subject: [R] Unbalanced ANOVA in R?

Hi all

I'm trying to complete a textbook example originally designed for SPSS
in R, and I therefore need to find out how to compute an unbalanced
ANOVA in R.

I did a search on the mailinglist archives an found a post by Prof.
Ripley saying one should use the lme function for (among other things)
unbalanced ANOVAs, but I have not been able to use this object.
My code gives me an error.. Why is that ?

aov(lme(DELAY ~ DOSE + TRIALS,data=epinuneq))
Error in getGroups.data.frame(dataMix, groups) :
Invalid formula for groups

Any ideas? How do I get an ANOVA computation that can handle uniqual
sampe sizes in R?

/Fredrik

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