How to interchange position of a matrix?

Question

Ammy 2022-9-14

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1805045-how-to-interchange-position-of-a-matrix

评论： Ammy 2022-9-14

采纳的回答： Stephen23

A = [3 1 2];

B = [2 3 1];

%%%%%

X = [2 1 3];

%%%

I want to interchange position of elements in X using A and B.

=> interchange 3rd element of X with 2nd element => X1 = [2 3 1 ]

=> interchange 1st element of X1 with its 3rd element => X2 = [1 3 2]

=> interchange 2nd element of X2 with its fisrt element => X3 = [ 3 1 2]

only need the last output that is X3.

I have tried the following

X(A) = X(fliplr(A))

But not getting how to use both A and B.

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Answer 1

Stephen23 2022-9-14

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1805045-how-to-interchange-position-of-a-matrix#answer_1053250

在 MATLAB Online 中打开

A = [3,1,2];
B = [2,3,1];
X = [2,1,3];
for k = 1:numel(X)
    X([A(k),B(k)]) = X([B(k),A(k)]);
end
X
X = 1×3
     3     1     2

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Ammy 2022-9-14

@Stephen23 thank you very much

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Answer 2

Torsten 2022-9-14

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1805045-how-to-interchange-position-of-a-matrix#answer_1053255

在 MATLAB Online 中打开

Are you sure that the changes should be performed subsequently with the new vectors obtained from the steps before ?

My guess would be that the 3rd element of X should be replaced by the 2nd element of X, the 1st element of X should be replaced with the 3rd element of X and the 2nd element of X should be replaced with the 1st element of X, resulting in [ 3 2 1].

If your interpretation is correct, use a loop:

A = [3 1 2];
B = [2 3 1];
X = [2 1 3];
for i = 1:numel(X)
    tmp = X(A(i));
    X(A(i)) = X(B(i));
    X(B(i)) = tmp;
end
X
X = 1×3
     3     1     2