Question

Suppose that I have an n row, m column matrix A, and I want to reorder every column in m according to the sorting of some specific row.

For instance, if I take order(A[,k]), that gives me the numeric or alphabetical order of elements in column k. I now want to sort every column in matrix A according to those rankings, so that elements 1...n in every row are ordered to correspond to elements 1...n (by rank) in column k. Is there a simple way to do this without looping over all columns?

Answer 1

Just use:

A[order(A[,k]),]

For example:

set.seed(21)
A <- matrix(rnorm(50),10,5)
A[order(A[,1]),]