Try this: > x <- matrix(runif(20), ncol=2) > x [,1] [,2] [1,] 0.33119833 0.4797847 [2,] 0.01339784 0.5218626 [3,] 0.78975940 0.8597246 [4,] 0.60849015 0.5217248 [5,] 0.91779777 0.9364047 [6,] 0.88302538 0.3467961 [7,] 0.87565986 0.4029147 [8,] 0.51594479 0.9885018 [9,] 0.87680383 0.7694989 [10,] 0.40761877 0.4661846
> apply(x, 1, function(y) ifelse(diff(y)<0, 1, 2)) [1] 2 2 2 1 2 1 1 2 1 2 -Christos > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Gundala Viswanath > Sent: Thursday, July 31, 2008 11:00 PM > To: [EMAIL PROTECTED] > Subject: [R] Grouping Index of Matrix Based on Certain Condition > > Hi, > > I have the following (M x N) matrix, where M = 10 and N =2 > What I intend to do is to group index of (M) based on this > condition of "x_mn" , namely > > For each M, > If x_m1 > x_m2, assign index of M to Group1 otherwise assign > index of M into Group 2 > > > > x > [,1] [,2] > [1,] 4.482909e-01 0.55170907 > [2,] 9.479594e-01 0.05204063 > [3,] 8.923553e-01 0.10764474 > [4,] 9.295003e-01 0.07049966 > [5,] 8.880434e-01 0.11195664 > [6,] 9.197367e-01 0.08026327 > [7,] 9.431232e-01 0.05687676 > [8,] 9.460356e-01 0.05396442 > [9,] 6.053829e-01 0.39461708 > [10,] 9.515173e-01 0.04848268 > > Is there a simple way to do it in R? > - Gundala Viswanath > Jakarta - Indonesia > > ______________________________________________ > 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.