How to multiply 4D array.

i want to multiply

L(:,:,k,:).*M(:,:,k,:);

i want to multiply without loop.

Answer 1

[Christine Tobler]

You could try downloading the tensor toolbox by Kolda and Bader, where this is provided as a command ttt(L, M, 3, 3). Alternatively, you can use the following code:

permL = permute(L, [3 1 2 4]);
permM = permute(M, [3 1 2 4]);
szL = size(L);
szM = size(M);
result = permL(:, :)'*permM(:, :);
result = reshape(result, [szL([1 2 4]), szM([1 2 4])]);

This returns a 6-dimensional array result, such that

result(i1, i2, i3, j1, j2, j3)

is the same as

a = 0; for k=1:size(L, 3), a = a + L(i1, i2, k, i3)*M(j1, j2, k, j3); end; a

Is this what you wanted to compute?

[Triveni]

plyangle = [45 45 45 45 45 45 0 0 0 0 0 0 0 0 45 45 45 45 45 45];
N1 = 2;
p1 = randi(numel(plyangle), [1 20 N1]);
plyangle = plyangle(p1);

for i= 1:2
    for k = 1:20
a(:,:,i,k)= cosd (plyangle(:,k,i));
b(:,:,i,k)= sind (plyangle(:,k,i));

      L(:,:,k,i) = [a(:,:,i,k)*b(:,:,i,k) 0 (a(:,:,i,k))^2;
                    0       0    b(:,:,i,k);
              a(:,:,i,k)*b(:,:,i,k)       0      0;];

      M(:,:,k,i) = [a(:,:,i,k)*b(:,:,i,k) 0 (a(:,:,i,k))^2;
                    0       0    b(:,:,i,k);
              a(:,:,i,k)*b(:,:,i,k)       0      0;];
      end
  end

can you correct this?? I think it's wrong.

[Christine Tobler]

I'm not sure what you want L and M to be, can you explain in more detail?

Answer 2

[Walter Roberson]

L.*M

Somehow I suspect that your question missed some information...