[R] Why aov() with Error() gives three strata?

[Jorge Fernando Saraiva de Menezes]

Bert, thanks for the reply but I feel that my question is less about
statistics and more about R interface. Specifically, because the output of
R seems different than other programs (systat, for example, gives a between
and a within table instead of a three level one).

I am familiar with the connection between mixed models and repeated
measures,and how mixed models are essentially replacing the aov models due
to their greater flexibility. But I feel that despite understanding a
little of the logic behind the mixed models that aov error terms seem
completely different to me than lmer randoms.

 I will post in those support lists you pass to me, if nothing comes from
here. However I had little luck in the stats exchange when I tried there.

About a local expert, I am once more in a corner. there are many people in
my department who excel in statistics. But I none use R, drastically
reducing their ability to explain to me the output of aov.

Em 28 de dez de 2017 20:04, "Bert Gunter" <bgunter.4567 at gmail.com> escreveu:

> Jorge:
>
> FYI, *generally speaking,* queries that are mostly statistical in
> nature, such as yours, are off topic here -- this list is about R
> programming help, not statistical help. Having said that, you still
> may get a useful response here -- the r-help/statistics intersection
> *is* nonempty. However, if not, 2.5 suggestions:
>
> 1. Try posting to r-sig-mixed-models instead. Repeated measures are a
> type of mixed/multilevel model and you may receive some useful
> suggestions there, including alternative R approaches to fitting such
> model (e.g. using lme() or lmer() ).
>
> 2. Alternatively, try posting to a statistics site like
> stats.stackexchange.com.
>
> 2.5. Or, if you can, the best idea might be to sit down with a local
> statistics expert.
>
> Cheers,
> Bert
>
>
>
> Bert Gunter
>
> "The trouble with having an open mind is that people keep coming along
> and sticking things into it."
> -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
>
>
> On Thu, Dec 28, 2017 at 7:52 AM, Jorge Fernando Saraiva de Menezes
> <jorgefernandosaraiva at gmail.com> wrote:
> > Dear list users,
> >
> > I am trying to learn Repeated measures ANOVA using the aov() interface,
> but
> > I'm struggling to understand its output.
> >
> > According to tutorials on the web, formula for a repeated measures design
> > is:
> >
> > aov(Y ~ IV+ Error(SUBJECT/IV) )
> >
> > This formula does work but it returns three strata (Error:SUBJECT, Error:
> > SUBJECT:IV, Error: Within), when I would expect two strata (Within and
> > Between subjects). I've seems some tutorials  show the exactly same
> setup,
> > but returning only the two first strata.
> >
> > Is it possible to have two or three strata depending on the data?
> > If there is always three strata, how this would fit the interpretation of
> > between vs within effects?
> >
> > Below a reproducible example that gives three strata:
> >
> > data(beavers)
> > data=data.frame(id =
> > rep(c("beaver1","beaver2"),c(nrow(beaver1),nrow(beaver2))),
> rbind(beaver1,beaver2))
> > data$activ=factor(data$activ)
> > #balance dataset to have 6 samples for every combination of beaver and
> > activity.
> > balanced = split(data,interaction(data$id,data$activ))
> > sizes = sapply(balanced,nrow)
> > selected = lapply(sizes,sample.int,6)
> > balanced = mapply(function(x,y) {x[y,]}, balanced,selected,SIMPLIFY=F)
> > balanced = do.call(rbind,balanced)
> > aov(temp~activ+Error(id/activ),data=balanced)
> >
> > Thanks,
> > Jorge
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
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> > PLEASE do read the posting guide http://www.R-project.org/
> posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
>

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