Re: [R] Summarizing a matrix

Hello, Better yet is function aggregate. # Create some data matrix Y <- matrix(c(sample(80, 507, TRUE), sample(-1:1, 4*507, TRUE)), ncol=5) X <- aggregate(Y[, 5]~Y[, 1], Y, sum) # In your case Y[, 4] not Y[, 1] Hope this helps, Rui Barradas Em 05-06-2012 09:53, Özgür Asar escreveu: Hi, x<

Re: [R] Summarizing a matrix

Hi, x<-matrix(0,80,ncol=1) will create x matrix with all elements 0 (to be filled by the sums that you need) sum(y[y[,4]==1,5]) will calculate the sum of 5th column of y with 4th column=1 Similarly, sum(y[y[,4]==80,5]) will calculate the sum of 5th column of y with 4th column=80. You can