# File lib/ai4r/clusterers/diana.rb, line 86
      def cluster_diameter(cluster)
        diameter = 0
        cluster.data_items.each_with_index do |item_a, item_a_pos|
          item_a_pos.times do |item_b_pos|
            d = @distance_function.call(item_a, cluster.data_items[item_b_pos])
            diameter = d if d > diameter
          end
        end
        return diameter
      end