If you're not adverse to cbind-ing a1 and a2, you can use this: a1a2 <- cbind(a1, a2)
a3 <- t(apply(a1a2, 1, function(x) x[order(x[1:ncol(a1)])+ncol(a1)])) Eric -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Timothy W. Hilton Sent: Thursday, July 31, 2008 2:19 PM To: r-help@r-project.org Subject: [R] sort rows of matrix by rows of another matrix Hello all, I am trying to sort rows of one matrix by rows of another. Given a1 and a2: ------ > a1 [,1] [,2] [,3] [1,] 7 6 8 [2,] 4 2 4 [3,] 4 7 2 [4,] 0 3 8 a1 <- structure(c(7, 4, 4, 0, 6, 2, 7, 3, 8, 4, 2, 8), .Dim = c(4L, 3L)) > a2 [,1] [,2] [,3] [1,] 101 102 103 [2,] 101 102 103 [3,] 101 102 103 [4,] 101 102 103 a2 <- structure(c(101L, 101L, 101L, 101L, 102L, 102L, 102L, 102L, 103L, 103L, 103L, 103L), .Dim = c(4L, 3L)) ------ I want to get a3: > a3 [,1] [,2] [,3] [1,] 102 101 103 [2,] 102 101 103 [3,] 103 101 102 [4,] 101 102 103 where the rows of a3 are the rows of a2 sorted according to the rows of a1. I can get the necessary sorting index: > apply(a1, 1, order) [,1] [,2] [,3] [,4] [1,] 2 2 3 1 [2,] 1 1 1 2 [3,] 3 3 2 3 and I can get the rows of a1 sorted according to the rows of a1: > t(apply(a1, 1, function(x) x[order(x)])) [,1] [,2] [,3] [1,] 6 7 8 [2,] 2 4 4 [3,] 2 4 7 [4,] 0 3 8 but I can't get the rows of a2 sorted according to the rows of a1... Thanks, Tim ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
