# File lib/ai4r/clusterers/single_linkage.rb, line 168
      def get_closest_clusters(index_clusters)
        min_distance = 1.0/0
        closest_clusters = [1, 0]
        index_clusters.each_index do |index_a|
          index_a.times do |index_b|
            cluster_distance = read_distance_matrix(index_a, index_b)
            if cluster_distance < min_distance
              closest_clusters = [index_a, index_b]
              min_distance = cluster_distance
            end
          end
        end
        return closest_clusters
      end