Nested for loops to compile all possible combinations of two vectors

Question

iontrap 2023-8-14

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2008467-nested-for-loops-to-compile-all-possible-combinations-of-two-vectors

评论： iontrap 2023-8-14

I have two vectors and would like to acquire the result of an operation using each combination of the two arrays. The result should look something like this:

1 2 2

1 4 4

1 6 6

2 2 4

2 4 8

... etc.

if vector1 = [1 2 3 ...] and vector2 = [2 4 6 .....].

Here is my attempt:

count = 0;
for i = 1:1:I
    for j = 1:1:J
        
        % 
        alpha = 0.038*i - 8;
        thresh = 0.00189*j + 0.01;
        
        % perform some operation to acquire chi
        
        chi = alpha  * thresh
        
        % save the chi into a matrix in the order of acquisition
        count=count+1;
        
        chi(:,count) = chi % this seems to give the correct 1x(I*J) array
        
        % save all 3 columns into array for the corresponding chi. this is not working. Nearly all entries are 0. 
        
        C=zeros(I*J,3);
        C(1,count) = alpha;
        C(2,count) = threshold;
        C(3,count) = chi;
        
    end
    count = count + J;
end

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Answer 1

Bruno Luong 2023-8-14

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https://ww2.mathworks.cn/matlabcentral/answers/2008467-nested-for-loops-to-compile-all-possible-combinations-of-two-vectors#answer_1287442

在 MATLAB Online 中打开

vector1 = [1 2 3 ];
vector2 = [2 4 6 ];
[V1, V2] = meshgrid(vector1, vector2);
A = [V1(:), V2(:), V1(:).*V2(:)]
A = 9×3
     1     2     2
     1     4     4
     1     6     6
     2     2     4
     2     4     8
     2     6    12
     3     2     6
     3     4    12
     3     6    18

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iontrap 2023-8-14

Thank you.

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Answer 2

Steven Lord 2023-8-14

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2008467-nested-for-loops-to-compile-all-possible-combinations-of-two-vectors#answer_1287452

在 MATLAB Online 中打开

If upgrading to release R2023a or later were an option you could use the combinations function.

vector1 = [1 2 3 ];
vector2 = [2 4 6 ];
results = combinations(vector1, vector2)
results = 9×2 table
    vector1    vector2
    _______    _______

       1          2   
       1          4   
       1          6   
       2          2   
       2          4   
       2          6   
       3          2   
       3          4   
       3          6   