[R] Contrasts for MANOVA

[Prof Brian Ripley]

On Fri, 19 Dec 2003, Andy Bunn wrote:

> A colleague asked me if R can do contrasts for MANOVA. SAS will using
> PROC GLM with CONTRAST but can R? I assured her that R can do everything
> but make coffee. If this is trivial then I apologize in advance.

Depends what you mean: I don't believe that SAS command does what I 
understand by manova, at least as its main purpose.

Both lm() and aov() handle multiple responses.

aov() in R is really set up to consider terms, but its summary method can 
split terms (via its `split' argument).

What summary.manova does which the other aov methods does not is to
compute multivariate test statistics for each term.  If your colleague
wants both the splitting allowed in summary.aov and the multivariate test
statistics of summary.manova then that is not currently supported. What I
would do there is to is ensure each of the contrasts I wanted had a
separate term in the model, and then use summary(manova(...)).

As ever, an example of what you want would help, as I have been guessing 
rather.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595