[R] [package-car:Anova] extracting residuals from Anova for Type II/III Repeated Measures ?

[John Fox]

Dear Peter,

Yes, you're absolutely right -- of course (though I didn't notice it!), the
precedence of / and * in a formula is like division and multiplication in an
arithmetic expression. With this correction, the SSs and error SSs are
properly matched by aov(), producing the same F-tests as Anova().

Thank you,
 John


> -----Original Message-----
> From: Peter Dalgaard [mailto:p.dalgaard at biostat.ku.dk]
> Sent: February-20-09 6:06 PM
> To: John Fox
> Cc: 'Tal Galili'; r-help at r-project.org
> Subject: Re: [R] [package-car:Anova] extracting residuals from Anova for
Type
> II/III Repeated Measures ?
> 
> John Fox wrote:
> > Dear Tal,
> >
> > I didn't have time to look at all this yesterday.
> >
> > Since aov() doesn't do what I typically want to do, I guess I've not
paid
> > much attention to it recently. I can see, however, that you appear to
have
> > specified the error strata incorrectly, since (given your desire to
compare
> > to Anova) the within-block factors are nested within blocks. Something
like
> >
> >> npk.aovE <- aov(value ~  N*P*K + Error(block/N*P*K), npk.long)
> >
> > should be closer to what you want, and in fact produces all of the sums
of
> > squares, but doesn't put all of the error terms together with the
> > corresponding terms; thus, you get, e.g., the test for N but not for P
and
> > K, even though the SSs and error SSs for the latter are in the table. By
> > permuting N, P, and K, you can get the other F tests. I suspect that
this
> > has to do with the sequential approach taken by aov() but someone else
more
> > familiar with how it works will have to fill in the details. I wonder,
> > though, whether you've read the sections in Statistical Models in S and
> MASS
> > referenced in the help file for aov.
> 
> Does it not help if you use Error(block/(N*P*K))? I suspect you're being
> bitten by operator precedence, of the same making as the fact that 1/2*2
> is 1, not 0.25.
> 
> 	-pd
> 
> --
>     O__  ---- Peter Dalgaard             Øster Farimagsgade 5, Entr.B
>    c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
>   (*) \(*) -- University of Copenhagen   Denmark      Ph:  (+45) 35327918
> ~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)              FAX: (+45) 35327907