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

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Marcus W
Marcus W 2018-12-14
评论： Marcus W 2018-12-16
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!

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采纳的回答

James Tursa
James Tursa 2018-12-14
编辑：James Tursa 2018-12-14
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);

更多回答（1 个）

Bruno Luong
Bruno Luong 2018-12-14
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.

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