# swap elements in a matrix

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Giannakis Stoukas on 20 Mar 2015
Commented: the cyclist on 10 May 2018
Hello i want to swap elements in a matrix.I want to do it to elements of the same row and to elements of differents rows. Please help.Thank you
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Giannakis Stoukas on 20 Mar 2015
To be more specific i want to execute local search to a matrix like this one
A=[1 4 7 16 32 48 1;
1 5 6 23 1 0 0;
1 9 31 8 2 1 0;
1 11 19 66 1 0 0]
The the elements of the matrix are arcs(for example 9-31 is the arc between nodes 9 and 31),so i want to make enough exchanges to reduce the cost.I can do exchanges of the same row like the 9 with 31 and i will the 3 row 1 31 9 8 2 1 0 and the other rows as they were,and i can do exchanges of different rows like the node 9 with the node 11. Is there any command to swap,or i have to use temp variables?

the cyclist on 20 Mar 2015
Edited: the cyclist on 10 May 2018
% A matrix:
A = magic(3);
% Swap the first and second elements of the first column:
A([1 2]) = A([2 1])
% Swap the first and second elements of the third column:
A([7 8]) = A([8 7])
% Swap the first and third elements of the first row:
A([1 7]) = A([7 1])
Note that I needed to take advantage of linear indexing.
the cyclist on 10 May 2018
Oops, there were actually a couple confusing typos in my post. I have edited to correct them. Thanks for pointing that out.

Ahamed Tuani on 13 Nov 2017
Hi,
I have been looking into local search as well. Giannakis, I know its quite q while ago but have you figure out how to do it?
The cyclist and fellow members, I have a question..say the path is 1-31-9-2-10-1..I want to swap 9 and 2 so that the new path will be 1-31-2-9-10-1. How can I do this? Tried indexing (maybe a dumb way) i.e init_tour((1:2):(4):(3):6) to get the new tour but its not working. Any help will be greatly appreciated. Thanks.