How can I swap two columns of a matrix in MATLAB?

How can I swap two columns of a matrix in MATLAB?

[David Sinex]

In a single line using fliplr() and given 2 indices idx1 & idx2,

idx1 = 2;
idx2 = 5;
AA(:,[idx1,idx2]) = fliplr(AA(:,[idx1,idx2]));

[Walter Roberson]

 idx1 = 2;
 idx2 = 5;

 AA(:,[idx1,idx2]) = AA(:,[idx2,idx1]);

Answer 1

[Manvi Goel]

There is an easy way to extract a column of a matrix in MATLAB

Suppose you have a matrix A:

A = [1, 2, 3 ; 4, 5, 6]

and you want to swap its first and the second columns.

The following can be done by extracting the first column, storing its value in a temporary variable and replacing second's value with the stored value:

v = A(:, 1);
A(:, 1) = A(:, 2);
A(:, 2) = v;

[Star Strider]

You can actually do that in one line:

A = [1, 2, 3 ; 4, 5, 6]
A = A(:,[2 1 3])

such that:

A =
     1     2     3
     4     5     6

A =
     2     1     3
     5     4     6

[Steven Lord]

There's a different way to do it in one line, though I'm going to split it across two lines to avoid duplicating the vector listing the columns to swap.

A = [1, 2, 3 ; 4, 5, 6]

% Two lines
v = [1 2];
A(:, v) = A(:, flip(v))

% One line
A(:, [1 2]) = A(:, [2 1]) % or
A(:, [1 2]) = A(:, flip([1 2]))

[Sterling Baird]

You can also use A = fliplr(A) if there are only two columns

[Andrea]

thanks! helped me as well. I hoped to take the product between the original matrix and a simple binary matrix which would perform the transformation but in my case the matrix is text cell so linear algebra operations are not possible (unless I am missing something)

[Walter Roberson]

It is not clear what 0 or false times a text entry would be ? Are you hoping, for example, that

false * "hello"

would give a result of "0" ?