# File lib/ai4r/som/two_phase_layer.rb, line 72
      def learning_rate_decay(epoch)
        if epoch < @phase_one
          @lr -= @delta_lr
          return @lr
        elsif epoch == @phase_one
          @lr = @phase_one_learning_rate
          @delta_lr = (@phase_one_learning_rate - @phase_two_learning_rate)/@phase_two
          return @lr
        else
          @lr -= @delta_lr
        end
      end