How to use CROSS with 3x1 Matrix on a 3xN Matrix

Hello,

I have 3x1 Matrix and want to do the CROSS of each element of a 3xN Matrix, to receive a 3xN Matrix as results.

Can I do this without a loop?

Thanks in advance!

Answer 1

[James Tursa]

Unfortunately, the cross( ) function does not auto-expand the dimensions of the operands. So you would have to manually do this or use a loop. E.g., if your vector is v and your matrix is M, then

result = cross(repmat(v,1,size(M,2)),M);

[Marcus W]

Thanks for your answer!

Answer 2

[Bruno Luong]

For my own use I have written this function

%%
function c = cross_dim1(a,b)
% Calculate cross product along the first dimension
c = zeros(size(a));
c(3,:) = a(1,:).*b(2,:)-a(2,:).*b(1,:);
c(1,:) = a(2,:).*b(3,:)-a(3,:).*b(2,:);
c(2,:) = a(3,:).*b(1,:)-a(1,:).*b(3,:);
end

If you have R2016b or ulterior it will do auto expansion.

[Marcus W]

Thanks a lot!