PDS/homework_1/matlab/dist2.m

function [D2] = dist2(X, Y)
% Calculates the squares of the distances of X and Y
%
% X: A Mxd array with m d-dimentional points
% Y: A Nxd array with n d-dimentional points
% d: Must be the same
%
% D2: The MxN matrix with the distances
%
    [~, d1] = size(X);
    [~, d2] = size(Y);
    if d1 ~= d2
        error('X,Y column dimensions must match');
    end
    % debug
    %X_norm = sum(X.^2, 2);
    %Y_norm = sum(Y.^2, 2)';
    %XY = 2 * X*Y';
    D2 = max(sum(X.^2, 2) - 2 * X*Y' + sum(Y.^2, 2)', 0);
    D2 = sqrt(D2);
    
end