# File lib/ai4r/clusterers/centroid_linkage.rb, line 55 def linkage_distance(cx, ci, cj) ni = @index_clusters[ci].length nj = @index_clusters[cj].length ( ni * read_distance_matrix(cx, ci) + nj * read_distance_matrix(cx, cj) - 1.0 * ni * nj * read_distance_matrix(ci, cj) / (ni+nj)) / (ni+nj) end