wolffd@0: function n2 = dist2(x, c)
wolffd@0: %DIST2	Calculates squared distance between two sets of points.
wolffd@0: %
wolffd@0: %	Description
wolffd@0: %	D = DIST2(X, C) takes two matrices of vectors and calculates the
wolffd@0: %	squared Euclidean distance between them.  Both matrices must be of
wolffd@0: %	the same column dimension.  If X has M rows and N columns, and C has
wolffd@0: %	L rows and N columns, then the result has M rows and L columns.  The
wolffd@0: %	I, Jth entry is the  squared distance from the Ith row of X to the
wolffd@0: %	Jth row of C.
wolffd@0: %
wolffd@0: %	See also
wolffd@0: %	GMMACTIV, KMEANS, RBFFWD
wolffd@0: %
wolffd@0: 
wolffd@0: %	Copyright (c) Ian T Nabney (1996-2001)
wolffd@0: 
wolffd@0: [ndata, dimx] = size(x);
wolffd@0: [ncentres, dimc] = size(c);
wolffd@0: if dimx ~= dimc
wolffd@0: 	error('Data dimension does not match dimension of centres')
wolffd@0: end
wolffd@0: 
wolffd@0: n2 = (ones(ncentres, 1) * sum((x.^2)', 1))' + ...
wolffd@0:   ones(ndata, 1) * sum((c.^2)',1) - ...
wolffd@0:   2.*(x*(c'));
wolffd@0: 
wolffd@0: % Rounding errors occasionally cause negative entries in n2
wolffd@0: if any(any(n2<0))
wolffd@0:   n2(n2<0) = 0;
wolffd@0: end