[R] Analyse the effect of group membership

[Tom Wright]

Hi,
Given a matrix
set.seed(500)
matrix(round(runif(100,0,1)),
	ncol=5,
	dimnames=list(Subject=1:20,
	Group=c('A','B','C','D','E')))

Is there an easy way to identify which combinations of groups exist,
i.e. subject2 is a member of group 'A+B+D+E' however no one is a member
of 'A+B+C+D'.

I want to analyze if particular combinations of groups have worse
outcomes than others. I admit I'm not really sure how to do this, if
anyone has any pointers I'll be happy to hear them.

Thanks,
Tom