Matrix of two columns using two vectors

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Juan Pérez Álvarez 2022-2-12

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1648615-matrix-of-two-columns-using-two-vectors

评论： Juan Pérez Álvarez 2022-2-14

采纳的回答： Voss

在 MATLAB Online 中打开

Hi. I need code for coordinate points (I need the program to always create a matrix(n,2) with two columns):

For example

A = [1,2,3,4];
B = [5,6,7];
LA = length(A);
LB = length(B);
Matrix  = [(1,5) ; (1,6) ; (1,7) ; (2,5) ; (2,6) ; ...];

As you can see, I need to multiply each element of vector A for each element of B. And I need to do this using for loops.

I know the Matrix has a length of LA*LB, then:

Matrix = zeros(LA*LB,2);

The question is how put every combination of the arrays to the matrix?

I reed a question in this forum to solve this kind of problem doing somethng like this:

Matrix = []
for i =1:LA
    for j =1:LB        
        Matrix = [Matrix B]; % Something like this        
    end
end

¿Any idea?

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Answer 1

Voss 2022-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/1648615-matrix-of-two-columns-using-two-vectors#answer_894800

在 MATLAB Online 中打开

A = [1,2,3,4];
B = [5,6,7];
LA = length(A);
LB = length(B);
Matrix = zeros(LA*LB,2); 
for i = 1:LA
    for j = 1:LB
        Matrix((i-1)*LB+j,:) = [A(i) B(j)];
    end
end
disp(Matrix);
     1     5
     1     6
     1     7
     2     5
     2     6
     2     7
     3     5
     3     6
     3     7
     4     5
     4     6
     4     7

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Voss 2022-2-12

编辑：Voss 2022-2-12

在 MATLAB Online 中打开

There are also many ways that do not use loops:

A = [1,2,3,4];
B = [5,6,7];
[A,B] = meshgrid(A,B);
Matrix = [A(:) B(:)];
disp(Matrix);
     1     5
     1     6
     1     7
     2     5
     2     6
     2     7
     3     5
     3     6
     3     7
     4     5
     4     6
     4     7
A = [1,2,3,4];
B = [5,6,7];
LA = length(A);
LB = length(B);
Matrix = [repelem(A(:),LB,1) repmat(B(:),LA,1)];
disp(Matrix);
     1     5
     1     6
     1     7
     2     5
     2     6
     2     7
     3     5
     3     6
     3     7
     4     5
     4     6
     4     7
A = [1,2,3,4];
B = [5,6,7];
LA = length(A);
LB = length(B);
Matrix = [kron(A(:),ones(LB,1)) repmat(B(:),LA,1)];
disp(Matrix);
     1     5
     1     6
     1     7
     2     5
     2     6
     2     7
     3     5
     3     6
     3     7
     4     5
     4     6
     4     7

And many others.

Juan Pérez Álvarez 2022-2-14

Thank you.

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Matrix of two columns using two vectors

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Matrix of two columns using two vectors

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