Multiplication of matrix and first dimension of a 3-D array without for loops

Hi,

I'm fairly new to Matlab but I was wondering if there is a way to multiply a 2-D matrix by the first dimension of a 3-D array without using for loops, and obtain another 3-D array.

The matrix, let's call it A, would be something like A(n,n), while the 3-D would be something like B(n,l,k). What I would like to do is somehow multiple A(n,n)*B(n,l,k) for every value of l and k, without going through two for loops.

Example below

A = rand(4,4);
B = rand(4,10,5);

for i = 1:10
    for j = 1:5
    C(:,i,j) = A(:,:)*B(:,i,j);
    end
end

Thanks

[Rik]

Why exactly do you want to remove the loop? And are you aware you're doing a matrix multiplication instead of an element-wise multiplication?

Answer 1

[Bruno Luong]

A = rand(4,4);
B = rand(4,10,5);

% orginal code
for i = 1:10
    for j = 1:5
    C(:,i,j) = A(:,:)*B(:,i,j);
    end
end

% one loop code
Coneloop = zeros(size(A,1),size(B,2),size(B,3));
for j = 1:size(B,3)
    Coneloop(:,:,j) = A*B(:,:,j);
end

% no loop code
Cnoloop = pagemtimes(A,B);

% Check matching
norm(Coneloop(:)-C(:),'Inf')

ans = 4.4409e-16

norm(Cnoloop(:)-C(:),'Inf')

ans = 4.4409e-16

norm(Cnoloop(:)-Coneloop(:),'Inf')

ans = 0

Answer 2

[Matt J]

C=reshape(  A*B(:,:)  , size(B));