get_maximum_by_stack (Gruff::Base::StackedMixin)

    # File lib/gruff/stacked_mixin.rb, line 7
      def get_maximum_by_stack
        # Get sum of each stack
        max_hash = {}
        @data.each do |data_set|
          data_set[DATA_VALUES_INDEX].each_with_index do |data_point, i|
            max_hash[i] = 0.0 unless max_hash[i]
            max_hash[i] += data_point.to_f
          end
        end

        # @maximum_value = 0
        max_hash.keys.each do |key|
          @maximum_value = max_hash[key] if max_hash[key] > @maximum_value
        end
        @minimum_value = 0
      end