MATLAB: Vector Matrix multiplication (Row wise)

matrixmultiplicationvector

Hi, I need to multiply each row of very large matrix with a row of corresponding vector. I don't really want to use for loop for that, i.e.,

N=15000;
L=rand(N,N); V=rand(N,1);
for i=1:1:N
L(i,:)=V(i)*L(i,:);
end

is it possible to do this in vectorized way?

Thank you

Erdem

Best Answer

 L = L.*repmat(V, [1 N]);

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MATLAB: How to vectorize the for loop

 u(j,1,1) = v(j) .* w(j,1,1);

The .* means element-by-element multiplication; otherwise, it attempts matrix multiplication.

MATLAB: Find sequence of values in matrix (row wise)

I solved the problem this way so far:

% Get cell array with non zero values:
rsm=sort(RCX');
[~,J,values]=find(rsm);
u=unique([J,values],'rows');
N=size(u,1);
tmp=diff([0;find(diff(u(:,1)));N]);
out1=mat2cell(u(:,2),tmp);
RCXcell=out1;
clear out1 rsm rsm0 u N tmp
% find complete rows as sequence in other rows
delVec=zeros(size(RCX,1),1);
for i=1:size(RCX,1)
    for j=1:size(RCX,1)
        Index=strfind(RCX(j,:),RCXcell{i}');
        if ~isempty(Index) && j~=i
            delVec(i)=1;
        end
    end
end
k=find(delVec);
RCX(k,:)=[];

It works for my purpose because the fields are not that big, but still not happy using two loops,

Anyway still not found an other more advanced solution. Which could be faster and usable for big fields

Best regards!

Best Answer

Related Solutions

MATLAB: How to vectorize the for loop

MATLAB: Find sequence of values in matrix (row wise)

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