[R] manova with Error?

[Peter Dalgaard BSA]

"RenE J.V. Bertin" <rjvbertin at hotmail.com> writes:

> Let's say I have a within-subject experiment with 2 observables, obs1 and ob2 and 2 independent factors, fac1 and fac2.
> 
> I can do
> 
> summary( aov( obs1~fac1*fac2 + Error(Subject/(fac1*fac2)) ) )
> summary( aov( obs2~fac1*fac2 + Error(Subject/(fac1*fac2)) ) )
> 
> to test the 2 observables separately.
> 
> > summary( fit<-manova( cbind(obs1,obs2)~fac1*fac2 + Error(Subject/(fac1*fac2)) ) )
> 
> gives results that seem sensible, but that I suppose represent the
> effects on obs1 and obs2 combined. The example for summary.manova
> shows that > summary.aov(fit) would print the effects separately for
> each observable. However, I get the message
> 
> Error in 1:object$rank : NA/NaN argument
> 
> and
> > class(fit)
> [1] "aovlist" "listof"
> 
> 
> I suppose that this means that I shouldn't want to do this sort of
> test, and rather look at each observable separately. The question
> is: why? Is there a simple explanation comprehensible for the
> non-statistician?

This is not my specialty, but could it be that you have an empty error
stratum? I.e. if Subject:fac1:fac2 is the entire data set, then there
is no DF for the residual error. (If so, try Error(Subject/(fac1+fac2)) )

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907
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