[R] crosstab means

[Heberto Ghezzo]

I would like to obtain a crosstabulation of means(var, quantiles...)
i.e. I have a data frame with Var-i, Var-j, Var-k, Var-X, var-Y
I like to have the mean of Var-X for each combination of Var-i,Var-j.
One solution would be:
by(var-i,Var-j,mean(Var-x))
but I would like it better formatted and with mean,S.Dev,n for each 
cell?
Does anybody have some function to do this or some ideas how to go 
about it?
Thanks.
..
R. Heberto Ghezzo  Ph.D.
Meakins-Christie Labs
McGill University
Montreal - Canada
heberto at meakins.lan.mcgill.ca
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