Simple way to delete a matrix column in Mathematica

Question

I am trying to delete both a matrix in mathematica. An inelegant way of doing it is as I do below, i.e specifying it in a new matrix as

S = Table[
    Ss[[If[i < t, i, i + 1]]][[If[j < t, j, j + 1]]], {i, q}, {j, q}];

where the goal is to eliminate row and column t.

Indeed delete a line is easy Delete[Ss,t]. For the column column I suppose I could do

Transpose[Delete[Transpose[Ss,t]]]

My primary concern is to do it in a way that executes the fastest way possible.

More generally, is there a Mathematica operator that makes it as easy to slice and dice matrix columns as it is to do for rows without resorting to transpose?

Dr. belisarius Dr. belisarius · Accepted Answer · 2011-03-13T14:42:43

I think you are looking for:

Drop[Ss,{t},{t}]

Timings:

ClearAll["Global`*"];

First@Timing[a = RandomInteger[1000, {5000, 5000}];]
0.34

First@Timing[Drop[a, {2}, {2}]]
0.11

While

First@Timing[Transpose@Delete[Transpose@Delete[a, 2], 2]]
0.5

Simple way to delete a matrix column in Mathematica

1 Answers