The intuition can be captured by the following optimization: where ∈ (0, 1) is a regularization parameter, W is an affinity matrix such that W ij measures the "closeness" of δ i and δ j , and D is a diagonal matrix such that D ii = j∈I W ij .
we design the affinity matrix as follows: where d 0 > 0 and γ < 0 are parameters, and d(•) is a symmetric distance function for bins.