diffusionkernel.m

流形学习程序

function [Y] = diffusionKernel (X,sigmaK,alpha,d)
% **************  diffusionKernel function  **************
% Written by R. Coifman & S. Lafon.

D = L2_distance(X',X',1);
K = exp(-(D/sigmaK).^2);
p = sum(K);
p = p(:);
K1 = K./((p*p').^alpha);
v = sqrt(sum(K1));
v = v(:);
A = K1./(v*v');
if sigmaK >= 0.5
    thre = 1e-7;  
    M = max(max(A));
    A = sparse(A.*double(A>thre*M));
    [U,S,V] = svds(A,d+1);   %Sparse version.
    U = U./(U(:,1)*ones(1,d+1));
else
    [U,S,V] = svd(A,0);   %Full version.
    U = U./(U(:,1)*ones(1,size(U,1)));
end;
Y = U(:,2:d+1);