Distance between two set of points in space

Question

andrea 2022-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/1637045-distance-between-two-set-of-points-in-space

评论： David Hill 2022-1-27

Hello,

So I have a set of points in a matrix A 10x3 ( i.e 10 points with x,y,z coordinates) and another set of points in a matrix B 10x3. I want to find the distance between each point of A with each point of B whitout using a for loop.

Normally I would fix a point in A and compute all the distances with the points in B and then choose another point in A and do the same and so on. Is there a way to do it directly from the matrix A and B whitout a loop ?

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Answer 1

Matt J 2022-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/1637045-distance-between-two-set-of-points-in-space#answer_882645

distances = pdist2(A,B);

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Answer 2

David Hill 2022-1-26

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https://ww2.mathworks.cn/matlabcentral/answers/1637045-distance-between-two-set-of-points-in-space#answer_882600

Why no loop? Below is oneliner but has an internal loop.

C=arrayfun(@(x)vecnorm((A(x,:)-B)'),1:size(A,1),'UniformOutput',false);

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andrea 2022-1-27

Yes thank you for the answer, that's nice. I thought that there could have been a better way without using for loop (some kind of vectorization) because in the case I have lots of points a for loop starts to be very slow.