Rearrange an array based on a matrix

Question

luca 2019-10-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/483463-rearrange-an-array-based-on-a-matrix

评论： luca 2019-10-3

Given the following arrays

V= [4,2,4,2,1,1,4,2,1,2,6,2,2,4,6,1,2,6,2,2,2,6,8,8,7,7,8,7,7,7,7,8,7,7,6,6,9,9,9,8,8,8,9,8,9,8,9,8,9]

I want to randomly mix the vector but following a rule

In fact, given a matrix

M = [1 6 7 9;
     2 0 8 0;
     4 0 0 0]
 

I want to randomly mix the values in V that are in the same column of M mainting the same position in V. It means that a place take by 1 can be randomly substituted by a 2 or a 4. It's important that the position inside the array V doesn't change, what has to change is just the value. For what concerne 6, in this case we have only 6, so it will be the same. For what concerne 7 and 8, they will randomly mix inside the array V exchange their value but mantain the same position (same column index).

making an example with a shorter vector

V = [6 7 6 1 2 4 9 9 9 6 7 4 7 1]

I would like to obtain a random array like

V = [6 8 6 4 1 4 9 9 9 6 7 4 8 2]

for example in the fourth column we had a 1, with the random permutation I want to randomly subsituted 1 with 1,2 or 4 (based on M column).

I hope the request is clear.

May someone help me with this task?

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Answer 1

meghannmarie 2019-10-3

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/483463-rearrange-an-array-based-on-a-matrix#answer_394683

Would something like this work:

for i = 1:numel(V)
    [~,k] = find(M == V(i));
    col_v = M(:,k);
    col_v = col_v(col_v ~= 0);
    ridx = randi(numel(col));
    V(i) = col(ridx);
end