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

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sermet 2013 年 1 月 9 日
example; 1 2 3 2 4 6 3 6 9 2nd 3rd
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Jan 2013 年 1 月 9 日
Please, sermet, format your messages properly. Do you see that it is confusing? There is a "? Help" button on top of the mask to input message. Please read the instructions presented there.
Posting two questions about the same problem is called "double posting" and not liked in forums. Therefore this forum offers the possibility to edit a question in case of unclear formulations.

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### 採用された回答

Jan 2013 年 1 月 9 日
And:
m(:, [2,3]) = m(:, [3,2])

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### その他の回答 (2 件)

Image Analyst 2013 年 1 月 9 日
Another way:
column2 = m(:,2); % Save old column2.
m(:,2) = m(:,3); % Move col3 to col2.
m(:,3) = column2; % Make col3 the old col2
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Jan 2013 年 1 月 10 日
@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 2013 年 1 月 9 日
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.
helps?

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