Daniel@0: function D = setDistanceDODMKL(X, W, Ifrom, Ito)
Daniel@0: %
Daniel@0: % D = setDistanceDODMKL(X, W, Ifrom, Ito)
Daniel@0: %
Daniel@0: %   X       = d-by-n data matrix
Daniel@0: %   W       = m-by-m-by-n PSD matrix
Daniel@0: %   Ifrom   = k-by-1 vector of source points
Daniel@0: %   Ito     = j-by-1 vector of destination points
Daniel@0: %
Daniel@0: %   D = n-by-n matrix of squared euclidean distances from Ifrom to Ito
Daniel@0: %       D is sparse, and only the rows corresponding to Ifrom and
Daniel@0: %       columns corresponding to Ito are populated.
Daniel@0: 
Daniel@0:     [d,n,m]       = size(X);
Daniel@0:     L           = W.^0.5;
Daniel@0:    
Daniel@0:     D = 0;
Daniel@0:     for i = 1:m
Daniel@0:         for j = i:m
Daniel@0:             Vfrom       = bsxfun(@times, squeeze(L(i,j)), X(:,Ifrom,i) + X(:,Ifrom,j));
Daniel@0: 
Daniel@0:             if nargin == 4
Daniel@0:                 Vto     = bsxfun(@times, squeeze(L(i,j)), X(:,Ito,i) + X(:,Ito,j));
Daniel@0:             else
Daniel@0:                 Vto     = bsxfun(@times, squeeze(L(i,j)), X(:,:,i) + X(:,:,j));
Daniel@0:                 Ito     = 1:n;
Daniel@0:             end
Daniel@0: 
Daniel@0:             if i == j
Daniel@0:                 s = 0.5;
Daniel@0:             else
Daniel@0:                 s = 1;
Daniel@0:             end
Daniel@0: 
Daniel@0:             D = D + s * distToFrom(n, Vto, Vfrom, Ito, Ifrom);
Daniel@0:         end
Daniel@0:     end
Daniel@0: 
Daniel@0: end