[R] Repeated Measures MANOVA in R
Peter Dalgaard
p.dalgaard at biostat.ku.dk
Thu Nov 9 15:17:34 CET 2006
Chuck Cleland <ccleland at optonline.net> writes:
> A. Bolu Ajiboye wrote:
> > Can R do a repeated measures MANOVA and tell what dimensionality the statistical variance occupies?
> >
> > I have been using MATLAB and SPSS to do my statistics. MATLAB can do ANOVAs and MANOVAs. When it performs a MANOVA, it returns a
> > parameter d that estimates the dimensionality in which the means lie. It also returns a vector of p-values, where each p_n tests
> > the null hypothesis that the mean vectors lie in an n-1 dimensional space (0-D space implies same vector, 1-D space implies scaled
> > vectors that point in the same direction, etc...). However, MATLAB does not do repeated measures MANOVA. SPSS can do repeated
> > measures MANOVA but it does not return this dimension output. Hence, I'm trying to find an environment that will allow me to do
> > repeated measures MANOVA and determine the dimensionality of the space, before I spend several weeks trying to learn it.
> >
> > I know the dimensionality parameter is based upon the eigenvalues of the ratio of the different SSCP (sum of squares and cross
> > products) matrices, but a) I'm not sure how to calculate the SSCP matrices for repeated measures MANOVA, and b) once I get these
> > eigenvalues and convert them a Pillai-Bartlett or Wilk's-Lambda value, I don’t know how to convert to an f-statistic.
> >
> > Does anybody know how to do this or has repeated measures MANOVA in R (while returning the dimensionality parameter)? Thanks in
> > advance for your help.
>
> I don't know about the dimensionality parameter, but have a look at
> anova.mlm(). In particular, you might want to run example(anova.mlm)
> and study the output. Also, you might look at SSD() and
> summary.manova() in package stats.
Yep. You may also want to look at
http://www.pubhealth.ku.dk/bs/publikationer/rr-06-11.pdf/
(which is under revision for R News)
Re. dimensionality, it is not clear to me what exactly Matlab might be
doing and how (and I can't easily find it on the net, or so it seems).
--
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