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function m = sqdist(p, q, A)
% SQDIST Squared Euclidean or Mahalanobis distance.
% SQDIST(p,q) returns m(i,j) = (p(:,i) - q(:,j))'*(p(:,i) - q(:,j)).
% SQDIST(p,q,A) returns m(i,j) = (p(:,i) - q(:,j))'*A*(p(:,i) - q(:,j)).
% From Tom Minka's lightspeed toolbox
[d, pn] = size(p);
[d, qn] = size(q);
if nargin == 2
pmag = sum(p .* p, 1);
qmag = sum(q .* q, 1);
m = repmat(qmag, pn, 1) + repmat(pmag', 1, qn) - 2*p'*q;
%m = ones(pn,1)*qmag + pmag'*ones(1,qn) - 2*p'*q;
else
if isempty(A) | isempty(p)
error('sqdist: empty matrices');
end
Ap = A*p;
Aq = A*q;
pmag = sum(p .* Ap, 1);
qmag = sum(q .* Aq, 1);
m = repmat(qmag, pn, 1) + repmat(pmag', 1, qn) - 2*p'*Aq;
end
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