How to create a 2D reverse matrix

Hi, I'm wondering how to create a reversed numerical matrix. For example, if I have a convolution h[j,k] = [1 2 3; 4 5 6; 7 8 9] then reverse h[j,k] = h[-j-k] = [9, 8 7; 6 5 4; 3 2 1]. I'm aware that you can use rot90(h, 2) and a combination of fliplr and flipud to get the results of reverse h, but are there any more direct ways to get the reverse matrix? Thanks.

Answer 1

[John D'Errico]

Since you are willing to use tools like fliplr (as opposed to flip. Anyway, fliplr and flipud are more descriptive, so I kind of like them.) But then what is wrong with the simple:

H =  [1 2 3; 4 5 6; 7 8 9] 

H = 3×3

1 2 3 4 5 6 7 8 9

Hflip = fliplr(flipud(H))

Hflip = 3×3

9 8 7 6 5 4 3 2 1

which requires only 2 calls. Or, if you like a matrix multiply, you could do it as:

trans = flip(eye(3));
trans*H*trans

ans = 3×3

9 8 7 6 5 4 3 2 1

Answer 2

[David Hill]

a=[1 2 3; 4 5 6; 7 8 9];
reshape(flip(a(:)),size(a))

ans = 3×3

9 8 7 6 5 4 3 2 1