X=randn(100,3);

[mx, nx] = size(X);

M = sum(X, 1)/mx;              % centroid (mean)

Xc = X - M(ones(mx,1),:);      % subtract centroid of X

W = (Xc' * Xc)/(mx - 1);       % variance matrix

% The call to REAL here is only to remove ``numerical noise''.

D = real(sum((Xc / W) .* conj(Xc), 2));   % Mahalanobis distances

请问求马氏距离有没有什么条件，比如，要求在直角坐标系下求，谢谢了