I wanna replacing 2nd and 3rd column to each other. How can I write a command?

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example; 1 2 3 2 4 6 3 6 9 2nd 3rd
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Jan on 9 Jan 2013
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Accepted Answer

Jan on 9 Jan 2013
m(:, [2,3]) = m(:, [3,2])

More Answers (2)

Image Analyst
Image Analyst on 9 Jan 2013
Another way:
column2 = m(:,2); % Save old column2.
m(:,2) = m(:,3); % Move col3 to col2.
m(:,3) = column2; % Make col3 the old col2
Jan on 10 Jan 2013
@Image Analyst and Daniel: I believe that Matlab does not allocate an [n x 2] array for the right hand side m(:, [3,2]), but does something like Bruno did in his FEX: MinMaxSelection with the inplace shared subarray tricks. I will perform some tests with large arrays.

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Amith Kamath
Amith Kamath on 9 Jan 2013
Assuming I understand the question right, here is an example of how it could be done:
x = magic(5); % a random matrix for illustration.
l = 1:size(x,2); % get the number of columns of x.
l(2:3) = [3 2]; % setup index replacement.
y = x(:,l); % y will have the same elements as x, with rows 2 and 3 exchanged.


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