Permuting the rows of a matrix based on given a given permutation

[mcabbott]

@iamsuddhasattwa

But there is no way anyone can possibly understand from the documentation alone that lt=(x,y)->isless(x[2],y[2])) is supposed to mean ``by second column".

You can also write sortslices(A, dims=1, by=row->row[2]), although I agree it’s not super-obvious what’s going to happen.