Delete rows from a matrix using for loop

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Juan Pérez Álvarez
回答： Voss 2022-2-20
Hello, I need delete rows from a matrix based on a logical condition of an array using for loops:
I need delete rows from this matrix:
Matrix = [ 1,1 ; 1,2 ; 1,3 ; 2,1 ; 2,2 ; 2,3 ];
Based on this array:
Vec = [0,-0.5,-1,0.5,0,-0.5];
if any element of Vec is < 0, I need delete the index rows of this condition from the Matrix.
And I need a new matrix
MatrixAux = [1,1 ; 1,3 ; 2,2];
I try this code:
LM = length(Matrix);
MatrixAux [];
for i =1: LM
if Vec(i) < 0
MatrixAux(i,:) = Matrix(i,:);
end
end
Any idea?

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采纳的回答

Voss
Voss 2022-2-20
Ran in:
The MatrixAux in your example doesn't seem to correspond to the process you decribe. Maybe I'm misunderstanding, but it seems like you can do this (no for loops required):
Matrix = [ 1,1 ; 1,2 ; 1,3 ; 2,1 ; 2,2 ; 2,3 ];
Vec = [0,-0.5,-1,0.5,0,-0.5];
idx_to_delete = Vec < 0;
Matrix(idx_to_delete,:) = [];
disp(Matrix);
1 1 2 1 2 2
or more simply:
Matrix = [ 1,1 ; 1,2 ; 1,3 ; 2,1 ; 2,2 ; 2,3 ];
Vec = [0,-0.5,-1,0.5,0,-0.5];
Matrix(Vec < 0,:) = [];
disp(Matrix);
1 1 2 1 2 2

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