Here's an example. See ?order mt <- matrix(sample(1:20), ncol = 2) mt[order(mt[,1]),] Best, Erik Iverson ermimi wrote: > I have a matrix with 2 columns and n row. I need sort the matrix by the first > column but the second row must be sort in the same order that the first > column. Somebody know how I can sort this matrix. > Thanks very much