Weights are not supported: multistratum aov is designed for balanced
designs and uses projection for which weighting is inappropriate.
On Wed, 17 Dec 2008, Ingmar Visser wrote:
Dear R-help,
I'm facing a problem with defining a repeated measures anova with
weighted data.
Here's the code to reproduce the problem:
# generate some data
seed=11
rtrep <- data.frame(rt=rnorm(100),ti=rep(1:5,20),subj=gl
(20,5,100),we=runif(100))
# model with within factor for subjects/repeated measurements, no
problem
aov(rt~ti + Error(subj/ti),data=rtrep)
#model with weights and subj as between factor, ie ignoring repeated
measures,
#again, no problem
aov(rt~ti+subj,data=rtrep,weights=we)
#combination of above two: repeated measures AND weights
aov(rt~ti + Error(subj/ti),data=rtrep,weights=we)
The latter model gives an error (see report below), but only after
fitting it, ie the error is produced by the
print and summary methods of the aov objects.
Any guidance is appreciated, best, Ingmar
Error produced in printing the fitted aov object:
Call:
aov(formula = rt ~ ti + Error(subj/ti), data = rtrep, weights = we)
Note: The results below are on the weighted scale
Grand Mean: 0.112081
Stratum 1: subj
Terms:
ti Residuals
Sum of Squares 2.002826 10.869940
Deg. of Freedom 1 18
Residual standard error: 0.7771007
Estimated effects are balanced
Stratum 2: subj:ti
Terms:
ti Residuals
Sum of Squares 0.382535 5.540047
Deg. of Freedom 1 19
Residual standard error: 0.5399828
Estimated effects are balanced
Stratum 3: Within
Error in print.aov(xi, ...) :
dims [product 60] do not match the length of object [100]
In addition: Warning message:
In resid * wt^0.5 :
longer object length is not a multiple of shorter object length
Ingmar Visser
Department of Psychology, University of Amsterdam
Roetersstraat 15
1018 WB Amsterdam
The Netherlands
t: +31-20-5256723
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