[R] expression for index of pairwise combinations

[Pete Brecknock]

If I have understood correctly, then as an example for 4 columns how about
....

d=data.frame(C1=c(1,1,1,1,1),C2=c(2,2,2,2,2),C3=c(3,3,3,3,3),C4=c(4,4,4,4,4))

combs=combn(paste("C",seq_len(4),sep=""),2,simplify=FALSE)

one =  sapply(combs,function(x) d[x[1]])
two =  sapply(combs,function(x) d[x[2]])

ret = mapply(cbind,one,two)
colnames(ret) = paste("C",1:length(combs),sep="")

You will need to change seq_len(4) to seq_len(269) in the second line.

HTH

Pete
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