This function provides the edges of the similarity graph constructed by k-NNL.
nnlink_K(distance,K)A K by K matrix, which is the distance matrix on the distinct values and K is the number of distinct values with at least one observation in either group.
Set the value of k in "k-NNL" to construct the similarity graph.
An edge matrix representing a similarity graph on the distinct values with the number of edges in the similarity graph being the number of rows and 2 columns. Each row records the subject indices of the two ends of an edge in the similarity graph.