Matrix of two columns using two vectors
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Juan Pérez Álvarez
on 12 Feb 2022
Commented: Juan Pérez Álvarez
on 14 Feb 2022
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?
0 Comments
Accepted Answer
Voss
on 12 Feb 2022
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);
2 Comments
Voss
on 12 Feb 2022
Edited: Voss
on 12 Feb 2022
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);
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);
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);
And many others.
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