Non-repeating selection from sets

Question

Amir Mahmoudi 2023-12-27

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https://ww2.mathworks.cn/matlabcentral/answers/2064372-non-repeating-selection-from-sets

评论： Amir Mahmoudi 2023-12-28

A is 1 by a matrix, B 1 by b, and C 1 by c. D is supposed to be the set of all non-repeating selection of respectively A, B, and C columns. What would be the most economical code of triples extraction? Thanks.

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Answer 1

Dyuman Joshi 2023-12-27

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https://ww2.mathworks.cn/matlabcentral/answers/2064372-non-repeating-selection-from-sets#answer_1378732

编辑：Dyuman Joshi 2023-12-28

在 MATLAB Online 中打开

%Random data
A = 1:3;
B = 1:4;
C = 1:5;
D = {A, B, C}
D = 1×3 cell array
    {[1 2 3]}    {[1 2 3 4]}    {[1 2 3 4 5]}
n = numel(D);
%Preallocate
out = cell(1, n);
%Reverse order to get the lexicographical order when concatenating
[out{end:-1:1}] = ndgrid(D{end:-1:1});
%Concatenate and reshape the data corresponding to number of vectors
out = reshape(cat(n,out{:}),[],n);
disp(out)
   1     1
   1     2
   1     3
   1     4
   1     5
   2     1
   2     2
   2     3
   2     4
   2     5
   3     1
   3     2
   3     3
   3     4
   3     5
   4     1
   4     2
   4     3
   4     4
   4     5
   1     1
   1     2
   1     3
   1     4
   1     5
   2     1
   2     2
   2     3
   2     4
   2     5
   3     1
   3     2
   3     3
   3     4
   3     5
   4     1
   4     2
   4     3
   4     4
   4     5
   1     1
   1     2
   1     3
   1     4
   1     5
   2     1
   2     2
   2     3
   2     4
   2     5
   3     1
   3     2
   3     3
   3     4
   3     5
   4     1
   4     2
   4     3
   4     4
   4     5