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Computing distance between two set of points (under vectorized approach)

Asked by SC
on 3 Apr 2019
Latest activity Commented on by madhan ravi
on 3 Apr 2019
I have two matrices (two set of p-dimensional points), X1 and X2, which are n*p and m*p matrices. I want the final output Dist, whose i-j entries is the distance between row_i of X1 and row_j of X2 (i.e. inner product of the difference).
I want to do this in the vectorization way (avoid using for loop), since the actual matrix size is very big.
For p=2, the following can do the job (X1 is named as XY1 and X2 is named as XY2 in the example, since the dimension is 2 only):-
How can I do that, say for p=10? Many thanks!
function Dist=dist_matrix(XY1,XY2)
% input: both XY1 and XY2 have 2 columns
% input: XY1 and XY2 are not necessarily having same number of rows
X1=XY1(:,1);
Y1=XY1(:,2);
X2=XY2(:,1);
Y2=XY2(:,2);
f = @(hori,verti)(hori-verti);
Dist_X = bsxfun(f,X2',X1);
Dist_Y = bsxfun(f,Y2',Y1);
Dist=sqrt(Dist_X.^2+Dist_Y.^2);
end

  3 Comments

You can do the arithmetic operations directly since your using 2016b version no need to use bsxfun().
Thanks for your reply. But what's your exact meaning? For example, how to do the arithmetic operations directly for the below example?
A = [8; 17; 20; 24];
B = [0 10 21];
bsxfun(@(x,y)x+y,A,B)

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