You can try 'outer'. Here is a way to get the index combinations that you want in a character vector:
as.vector(outer(1:4, 1:4, paste, sep=",")) -Christos -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Mark Hempelmann Sent: Saturday, March 25, 2006 12:50 PM To: [email protected] Subject: [R] pairwise combinatons of variables Dear WizaRds, although this might be a trivial question to the community, I was unable to find anything solving my problem in the help files on CRAN. Please help. Suppose I have 4 variables and want to use all possible combinations: 1,2 1,3 1,4 2,3 2,4 3,4 for a further kmeans partitioning. I tried permutations() of package e1071, but this is not what I need. Thank you for your help and support. mark. --------------------------------------------------------------------- Additionally: For anybody who is willing to offer some advise, here is my complete approach: library(e1071) mat <- matrix( c(6,7,8,2,3,4,12,14,14, 14,15,13,3,1,2,3,4,2, 15,3,10,5,11,7,13,6,1, 15,4,10,6,12,8,12,7,1), ncol=9, byrow=T ) rownames(mat) <- paste("v", 1:4, sep="" ) tmat <- t(mat) cluster <- c(1, 2, 1, 3, 3, 3, 1, 2, 2) centroids <- matrix( 0, ncol=3, nrow=4 ) obj <- vector(mode="list", length=3) for (j in 1:4){ for (i in 1:3){ where <- which(cluster==i) # which obj is in which class? centroids[j,i] <- mean( tmat[ where,j ] ) obj[[i]] <- tmat[where,] } } colnames(centroids) <- paste( c("Cluster"), 1:3) rownames(centroids) <- rownames(mat) centroids obj ## now I want to do kmeans of all possible variable pairs, e.g. v1 and v3 ## automization in a second step later wjk <- kmeans(tmat[,c(1,3)], centers=centroids[c(1,3),], iter.max=10, algorithm="MacQueen") ## obviously wrong ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
