pdist2 output is larger than expected

 X= pdist2 (A,B, "chebychev")
 

A and B both are 3000x3 arrays (x,y,z data).

Why is X a 3000x3000 array rather than a 3000x1 array?

This seems to give the right answer though... why?

 Z =diag(pdist2 (A,B, "chebychev"));

Answer 1

[Dave B]

pdist2 is providing all the pairwise distances. It compares row 1 of A with row 1 of B (Z(1,1)), then row 1 of A with row 2 of B (Z(1,2) and Z(2,1)), etc. Along the diagonal are the matching row cases.

[Pelajar UM]

Thanks, but is there a function that would give only the diagonal values?

I could use the diag function to get this, but when A and B becomes very large, then I run out of memory.

[Dave B]

Chebyshev distance is the maximum distance across dimensions, right?

a=rand(10);
b=rand(10);
cheby_pdist2=diag(pdist2(a,b,'chebychev'))

cheby_pdist2 = 10×1

0.8386 0.6272 0.8585 0.6400 0.4895 0.8044 0.6681 0.7439 0.8985 0.7146

cheby_daveb=max(abs(a-b),[],2)

cheby_daveb = 10×1

0.8386 0.6272 0.8585 0.6400 0.4895 0.8044 0.6681 0.7439 0.8985 0.7146

[Pelajar UM]

Right. Thank you so much.