Trying to build an array of row vectors such that every possible combination of the 3 vector components is included

Question

Michael Costa 2021-5-7

0
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评论： Michael Costa 2021-5-7

Take a vector [i j k]. I want to build an array of such vectors, with each element ranging from 1:20, such that every possible combination of the elements is included in the array. For example, the array would start with [1 1 1], [2 1 1], [3 1 1], and continue until [20 20 20] is reached. Here is what I have started with.

clear;

Ax_A = [];

for i = 1:20

Ax_A(i,1) = i;

end

for j = 1:20

Ax_A(:,2) = j

end

for k = 1:20

Ax_A(:,3) = k

end

When I don't supress the output for the 2nd (jth) and 3rd (kth) elements, it seems to be iterating through every single combination that I want. However, it is not storing all of these in the whole array that I am trying to build. If I do suppress the outputs, the result is just a 20x3 with i = 1-20, j = 20, and k = 20.

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Answer 1

David Fletcher 2021-5-7

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https://ww2.mathworks.cn/matlabcentral/answers/824415-trying-to-build-an-array-of-row-vectors-such-that-every-possible-combination-of-the-3-vector-compone#answer_694660

编辑：David Fletcher 2021-5-7

If you are going the loop route, then you want all three loops to be nested, rather than three separate loops. Something more like this:

clear;
Ax_A = [];
for i = 1:20
    page=[];
   for j = 1:20
      for k = 1:20
          page=[page; k j i];
      end
   end
   Ax_A(:,:,i)=page;
end 