# File lib/ai4r/som/layer.rb, line 34
      def initialize(nodes, radius, epochs = 100, learning_rate = 0.7)
        raise("Too few nodes") if nodes < 3
        
        @nodes = nodes
        @epochs = epochs
        @radius = radius
        @time_for_epoch = @epochs / Math.log(nodes / 4.0)
        @time_for_epoch = @epochs + 1.0 if @time_for_epoch < @epochs

        @initial_learning_rate = learning_rate
      end