# What is the easiest way to remove a vector from a matrix?

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Cantor Set il 11 Set 2021
Commentato: Chunru il 15 Set 2021
Suppose there is a Loop A which returns a row vector y of the same number of columns such as matrix Q.
I want to remove all the occurrences of the row vectors y from Q, is their a simple way to do it (I am trying to avoid loops).
Here is a loop I wrote:
for i=1:size(Q,1)
s=eq(Q(i,:),y); r=all(s);
if r==1
Q(i,:)=[];
end
end
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### Risposte (2)

Chunru il 11 Set 2021
Modificato: Chunru il 11 Set 2021
a = magic(4);
a = [a; a(1, :); a]; % 1st 5th and 6th rows are the same
a
a = 9×4
16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1 16 2 3 13 16 2 3 13 5 11 10 8 9 7 6 12 4 14 15 1
y = a(1, :); % the vector input
idx = all(a == y, 2);
a(idx, :)=[]
a = 6×4
5 11 10 8 9 7 6 12 4 14 15 1 5 11 10 8 9 7 6 12 4 14 15 1
% in a line
% a(all(a==y, 2), :) =[]
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this removes the lines that correspond to the indices in idx
Chunru il 15 Set 2021
@Chad Greene You don't have to replicate y (matlab does auto array expansion).

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A = [magic(5); magic(5)];
v = A(1,:);
A(eqRows, :) = [];
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