Multiple swapping of rows and columns

Question

m={{a, b, c, p}, {d, e, f, x}, {g, h, k, z}, {u, v, w, y}};

I want to swap 1st and 2nd rows by 4th and 3rd rows respectively. And then, swap 1st and 2nd columns by 4th and 3rd columns.

I don't think it is obvious that Reverse has second argument, but if you need to reverse something it is easy to face it in docs :) So my point is that it should be closed, but let's see what community says :) — Kuba, Apr 29 '14 at 16:03
@Kuba Unless it's a dup (I don't know), I think you could post it as an answer — Dr. belisarius, Apr 29 '14 at 16:07

score 9 · Accepted Answer · edited Apr 13 '17 at 12:55

9

OK, encouraged by belisarius, here's the way.

If you know that Reverse exists you may use:

Reverse /@ Reverse @ m

then you could check the docs and realise that Reverse has 2nd argument:

Reverse[m, {1, 2}]

But if you don't but you are amazed by Span+Part you can end up with:

m[[;; , {4, 3, 2, 1}]][[{4, 3, 2, 1}]]

or even more Span: :)

m[[;; , -1 ;; 1 ;; -1]][[-1 ;; 1 ;; -1]]

Why is multidimensional Reverse slow? - nice question where I've learned about -1;;1;;-1

edited Apr 13 '17 at 12:55

Community

answered Apr 29 '14 at 16:14

Kuba

1

Congratulations on joining the 20K club! :-) For some reason I still think of you as a "new" member but you have become a pillar of the community, and not by "reputation" alone. – Mr.Wizard Apr 29 '14 at 23:35
@Mr.Wizard Thank you for those kind words :) I do enjoy being here :), almost each day I can learn, or at least face, something new so thank you community of Mathematica.SE :) – Kuba Apr 30 '14 at 05:12

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