How to multiply Multidimensional Arrays with a column vector

I want to multiply A with B so that C(:,:,1) is equal to A(:,:,1)*B(1) and C(:,:,2) is equal to A(:,:,2)*B(2)

>> A = cat(3, [2 8; 0 5], [1 3; 7 9])

A(:,:,1) =

     2     8
     0     5

A(:,:,2) =

     1     3
     7     9

>> B=[1 2]'

B =

     1
     2

I'm looking to get this:

>> C=???

C(:,:,1) =

     2     8
     0     5

C(:,:,2) =

     2     6
    14    18

Answer 1

[sixwwwwww]

Dear Tristan, here is the code which performs the task:

A = cat(3, [2 8; 0 5], [1 3; 7 9]);
B=[1 2]';
for i = 1:length(B)
    C(:, :, i) = B(i) * A(:, :, i);
end
disp(C)

I hope it helps. Good luck!

[Tristan]

is there any way to do it without using a loop?

[sixwwwwww]

I couldn't see any way to do it without loop. Maybe if I will have I will post here

[Tristan]

The only way I can think of would be by transforming B into a multidimensional array like this:

>> B(:,:,1)=1;B(:,:,2)=2

B(:,:,1) =

     1

B(:,:,2) =

     2

>> bsxfun(@times,A,B)

ans(:,:,1) =

     2     8
     0     5

ans(:,:,2) =

     2     6
    14    18

but the real B I'm working with has too many numbers to type them all, any idea how I could do it?

[sixwwwwww]

You can do it like this:

C = cat(3, [], [], B);

[Shambhavi Singh]

This should work too

C=A.*permute(B,[3 2 1]),3);

Permute switches the rows in B (So the elements of a column vector) with the third dimension

Answer 2

[James Tursa]

C = mtimesx(A,reshape(B,1,1,[]));

You can find MTIMESX here:

http://www.mathworks.com/matlabcentral/fileexchange/25977-mtimesx-fast-matrix-multiply-with-multi-dimensional-support

Answer 3

[Pavel Chmelar]

Clear Matlab solution according sixwwwwww and Tristan:

B=zeros(1,1,2);
B(:)=[1,2];
C=bsxfun(@times,A,B);