How do I swap the elements in the major diagonal with those in the minor diagonal?

So let's assume I have an array like so

x = 4x5 array

[1 2 3 4 5
 6 7 8 9 1 
 2 3 4 5 6
 7 8 9 1 2]

What I want to do is flip the diagonals of this matrix horizontally. So the end result would look like this,

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

As you can see, the diagonals starting from each corner going across have been flipped horizontally. 1 and 5 have swapped in the first row, 7 and 9 have swapped in the second row and so on. I tried indexing these values and then doing something like array(major) = array(minor) but this only brings back an error saying "Index exceeds the number of array elements. Could somebody help me?

Answer 1

[madhan ravi]

 ix1 = find(eye(size(x)));
 ix2 = sort(find(fliplr(eye(size(x)))), 'descend');

 x([ix1, ix2]) = x([ix2, ix1])

[Stephen23]

+1 madhan ravi: neat idea, with effective use of linear indices.

[madhan ravi]

Thank you Stephen!

Answer 2

[Stephen23]

Similar to madhan ravi's answer, without sorting:

>> x = [1,2,3,4,5;6,7,8,9,1;2,3,4,5,6;7,8,9,1,2]
x =
   1   2   3   4   5
   6   7   8   9   1
   2   3   4   5   6
   7   8   9   1   2
>> ix0 = eye(size(x));
>> ix1 = flipud(find(ix0));
>> ix2 = find(fliplr(ix0));
>> x([ix1;ix2]) = x([ix2;ix1])
x =
   5   2   3   4   1
   6   9   8   7   1
   2   3   4   5   6
   7   1   9   8   2

Works for character matrices too:

>> x = char('A'+x)
x =
FCDEB
GJIHB
CDEFG
HBJIC
>> x([ix1;ix2]) = x([ix2;ix1])
x =
BCDEF
GHIJB
CDEFG
HIJBC

Answer 3

[Bruno Luong]

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

s=size(x);
m=min(s);
n=s(2);
i=1:m;
id=sub2ind(s,i,i);
iad=sub2ind(s,i,n+1-i);
x([id iad])=x([iad id])

[Brett Baxter]

Would this flip arrays of characters as well?