How to run randperm command for 100 times and store these permutations

Question

lilly lord 2022-4-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1699420-how-to-run-randperm-command-for-100-times-and-store-these-permutations

评论： Voss 2022-4-19

Hi, I want to run randperm command to generate different permutations and save these permutation . The following code oly shows the last permutation. k contains only one permutation

N=10;T=4;
k=zeros(10,4);
for ii=1:T-1
Z = arrayfun(@(x)randperm(N),ii,'UniformOutput',0);
Z = cell2mat(Z);
k=Z;
end

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Answer 1

Voss 2022-4-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1699420-how-to-run-randperm-command-for-100-times-and-store-these-permutations#answer_945420

在 MATLAB Online 中打开

To save each permutation, assign it to a row or column of k, instead of overwriting k each time.

You've set up k to have 10 rows for permutations of length 10, so it looks like you want each permutation to be a column of k:

N=10;T=4;
% k=zeros(10,4);
k=zeros(N,T);
for ii=1:T-1
%     Z = arrayfun(@(x)randperm(N),ii,'UniformOutput',0);
%     Z = cell2mat(Z);
    Z = randperm(N); % this does the same thing as the two lines above
    k(:,ii)=Z;
end
k
k = 10×4
     1     4     5     0
     2     3     1     0
     6     9     6     0
     5     8     7     0
     4     1     4     0
    10     6     3     0
     8    10     2     0
     9     7     8     0
     7     2     9     0
     3     5    10     0

You can make each permutation be a row of k instead (here making T permutations instead of T-1):

N=10;T=4;
k=zeros(T,N);
for ii=1:T
    k(ii,:)=randperm(N);
end
k
k = 4×10
    10     5     9     1     7     8     4     2     3     6
    10     4     9     5     3     2     1     8     7     6
     2     9     8     1     5     6     4     3     7    10
     7     9     3     2    10     6     1     8     4     5

And this type of thing may have been what you were going for with arrayfun/cell2mat:

N=10;T=4;
k = cell2mat(arrayfun(@(x)randperm(N),1:T-1,'UniformOutput',0).')
k = 3×10
     1     2     5     3     8     4     6    10     7     9
     2     7     3     8     6     9     1    10     4     5
     3     2     8     1    10     7     6     9     5     4