Class: DecisionTree

Inherits:
Object
  • Object
show all
Defined in:
lib/decision-tree.rb

Instance Method Summary collapse

Constructor Details

#initialize(entries, columns = nil, algorithm = 'c45', dimension = nil, parent_node = nil, threshold = nil, path = nil) ⇒ DecisionTree

Returns a new instance of DecisionTree.



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# File 'lib/decision-tree.rb', line 30

def initialize(entries, columns=nil, algorithm='c45', dimension=nil, parent_node=nil, threshold=nil, path=nil)
	@parent_node = parent_node
	@path = if path.nil?
		Array.new
	else
		path
	end

       @threshold = threshold

       @algorithm = if algorithm=='c45' or algorithm=='id3'
           algorithm
       else
           raise "Unknown algorithm"
       end

	@dimension = if dimension.nil?
		entries[0][:features].size
	else
		dimension
	end

	@columns = if columns.nil?
		@dimension.times.map{|i| "feature_#{i}"}
	elsif columns.size != @dimension
		raise "The number of columns is incorrect"
	else
		columns
	end


	@labels = entries.map{|x| x[:label]}
	@entropy = @labels.entropy
	@child_nodes = Hash.new

	return if @path.size == @dimension
	return if @entropy==0.0

	@path << choose_best_feature(entries)

	build_child_nodes(entries)
end

Instance Method Details

#feature_index ⇒ Object 



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# File 'lib/decision-tree.rb', line 74

def feature_index
	@path[-1]
end

#feature_name ⇒ Object 



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# File 'lib/decision-tree.rb', line 79

def feature_name
	@columns[ @path[-1] ]
end

#to_pseudo_code(buff = nil, indent = "") ⇒ Object 



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# File 'lib/decision-tree.rb', line 83

def to_pseudo_code(buff=nil,indent="")
    buff = Array.new if buff.nil?

    if @child_nodes.size==0
        result = @labels.to_set.to_a
        if result.size==1
            buff << "#{indent}return #{result[0]}"
        else
            buff << "#{indent}return #{@labels}"
        end
    end

    @child_nodes.each do |feature_value,child_node|
        buff << "#{indent}if(#{feature_name} == #{feature_value}){"
        child_node.to_pseudo_code(buff, indent+"  " )
        buff << "#{indent}}"
    end
    return buff
end