Distance between ALL(all combinations) points of matrix

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Lidziya Semeniuk
Lidziya Semeniuk el 19 de Oct. de 2019
Respondida: Rik el 19 de Oct. de 2019
How can i have a vector which consists of all the distances betweeen all points of matrix? I have 3D matrix B = 151*3 with points coordinates (X,Y,Z are columns). Possible combination of all this points should be 11325(n = 151,k=2). Snímek obrazovky 2019-10-19 v 14.33.27.png
`I can calculate the distance between 2 3d points like this:
dist = norm(B(1,:,:)-B(2,:,:))
but unfortunately my for loop doesn't work:
n = size(B,1)
for k = 1:n-1
for a = k:n-1;
Z1 = B(k,:,:);
Z2 = B(a+1,:,:);
dist = norm(Z2 - Z1);
end
end
it returns only one number , but i want to have a vector with all distances, so i can make a histogram from it.
Where is the mistake of the for loop? Or can i solve this with repmat function?
Thank you!

Respuesta aceptada

Rik
Rik el 19 de Oct. de 2019
Note that you are not calculating only unique combinations. The reason you are only getting a single value is that you are not indexing your output variable.
What you should do is generate the matrix of indices of the combinations and then loop through that matrix. You can use nchoosek to create the matrix.

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