swap elements in a matrix

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

[Adam]

An example would be useful, although the usual method for swapping elements is to use a temporary variable to store one while you copy the other over the top of it and then copy from the temporary variable into the 2nd location.

[Giannakis Stoukas]

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?

Answer 1

[the cyclist]

% 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.

[Giannakis Stoukas]

Thank you for your respond.It is not exactly what i want to do.I have answerd previous what i want.More specifically i have a matrix of arcs and i want to execute local search exchanges to minimize the cost (that i have in different variable).

[the cyclist]

You can use my technique, as long as you understand the linear indexing page I cited.

For example, to swap 9 and 31 in your example, use

A([11 7]) = A([7 11])

The number 9 is in the 7th position (using linear indexing), and the number 31 is in the 11th position.

[YANAN ZHU]

A([1 7]) = A([7 1]) actually swap the first and third elements of the first row, not "Swap the first and second elements of the first row"

[the cyclist]

Oops, there were actually a couple confusing typos in my post. I have edited to correct them. Thanks for pointing that out.

Answer 2

[Ahamed Tuani]

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.