Azzera filtri
Azzera filtri

issue in matrix multiplication

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mary
mary il 4 Dic 2013
Risposto: Walter Roberson il 5 Dic 2013
G=[1 1 1 1 1 0 0 0 1 0 0 0; 0 0 1 1 0 0 0 1 0 1 0 0; 1 1 1 0 1 0 0 1 0 0 1 0; 1 0 0 1 1 1 0 1 0 0 0 1];
m=[1 0 1 0]
how to multiply them??

Risposta accettata

Youssef  Khmou
Youssef Khmou il 4 Dic 2013
Modificato: Youssef Khmou il 4 Dic 2013
G is 4x12 and m is 1x4, then two possibilities :
m*G
G'*m'
You do not get binary result because of the multiplication cij=sum a_ik b_kj there is an addition. you can get binary results if the matrices have the same dimensions and you use Hadamard product :
m=m'
M=zeros(4,12);
for n=1:12
M(:,n)=m;
end
M.*G

Più risposte (4)

Wayne King
Wayne King il 4 Dic 2013
Modificato: Wayne King il 4 Dic 2013
G=[1 1 1 1 1 0 0 0 1 0 0 0; 0 0 1 1 0 0 0 1 0 1 0 0; 1 1 1 0 1 0 0 1 0 0 1 0; 1 0 0 1 1 1 0 1 0 0 0 1];
m=[1 0 1 0];
out = m*G;
How else would you presume to multiply them?
  1 Commento
mary
mary il 4 Dic 2013
when i multiplied them using this way the result will be [ 2 2 3 2 2 0 0 2 1 1 1 0]

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Walter Roberson
Walter Roberson il 4 Dic 2013
G is 12 x 4, and m is 1 x 4, so there is no direct way to multiply them. You can, however, use
G * m.'
to get 12 x 1, or you can use
m * G.'
to get 1 x 12
Possibly what you want is
G .* repmat(m.', 1, size(G,2))
  1 Commento
mary
mary il 4 Dic 2013
G is 4 by 12 if i multiply them directly the result is not binary ?? how come??

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sixwwwwww
sixwwwwww il 4 Dic 2013
mary you can get desired output as follows:
G = [1 1 1 1 1 0 0 0 1 0 0 0; 0 0 1 1 0 0 0 1 0 1 0 0; 1 1 1 0 1 0 0 1 0 0 1 0; 1 0 0 1 1 1 0 1 0 0 0 1]';
m = [1 0 1 0];
idx = find(m);
result = zeros(1, size(G, 1));
for i = 1:size(G, 1)
result(i) = sum(G(i, min(idx):max(idx)));
end
disp(result)
Do you need this?
  1 Commento
mary
mary il 4 Dic 2013
not this i need the result in binary .. just multiplying two matrices and the result would be binary

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Walter Roberson
Walter Roberson il 5 Dic 2013

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