PDS_kNN/matlab/distXY.m

function D = distXY(X, Y)
%distXY Calculate an m x n Euclidean distance matrix D of X and Y
%
% Calculate an m x n Euclidean distance matrix D between two set
% points X and Y of m and n points respectively
%
% X : [m x d]   Corpus data points (d dimensions)
% Y : [n x d]   Query data points (d dimensions)
% D : [m x n]   Distance matrix where D(i,j) the distance of X(i,:) and Y(j,:)

    [m, d1] = size(X);
    [n, d2] = size(Y);
    if d1 == d2
        d = d1;
    else
        error('Corpus(X) and Query(Y) data points must have the same dimensions (d)');
    end
    D = (X.*X) * ones(d,1)*ones(1,n) -2 * X*Y.' + ones(m,1)*ones(1,d) * (Y.*Y).';
    %D = sum(X.^2, 2) - 2 * X*Y.' + sum(Y.^2, 2).'
    D = sqrt(D);
end