Class: BNTPGFromPositiveNegativeRelations

Inherits:
BnTableProbabilitiesGenerator show all
Defined in:
lib/bn4r/bn_table_probabilities.rb

Overview

Bayes Net Table Probabilities Generator from Positive Negative Relations

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from BnTableProbabilitiesGenerator

#get_node_probability_from_boolean_combination

Class Method Details

.get_node_probability_from_boolean_combination(boolean_combination, type_of_position_impact) ⇒ Object

returns P(node=yes| parents=boolean_combination) where parents have relations with the node showed in type_of_position_impact type_of_position_impact is a array of boolean values showing the relation ( positive | negative ) beetwen the node and its parents.



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# File 'lib/bn4r/bn_table_probabilities.rb', line 56

def self.get_node_probability_from_boolean_combination(boolean_combination, type_of_position_impact)
  num_eq = 0.0
  boolean_combination.size.times { |i|
    num_eq += 1.0 if type_of_position_impact[i] && boolean_combination[i]
    num_eq += 1.0 if !type_of_position_impact[i] && !boolean_combination[i]
  }
  num_eq / boolean_combination.size.to_f
end

Instance Method Details

#table_probabilities_for_node(node, type_of_position_impact) ⇒ Object

type_of_position_impact is a array of boolean values showing the relation ( positive | negative ) beetwen the node and its parents.



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# File 'lib/bn4r/bn_table_probabilities.rb', line 25

def table_probabilities_for_node(node, type_of_position_impact)
  raise "Node parents and type_of_position_impact with different size" if node.parents.size != type_of_position_impact.size
  boolean_combinations = []
  (2**node.parents.size).times { |i|
    boolean_combination = Array.new(node.parents.size, false)
    actual_value = i
    (node.parents.size).times { |j|
      boolean_combination[j] = !(actual_value%2 == 0)
      actual_value = actual_value / 2
    }
    boolean_combinations << boolean_combination
  }
  #p boolean_combinations
  table_probabilities = [] # Array.new(2**(node.parents.size+1))
  boolean_combinations.each { |boolean_combination|
    [true,false].each { |node_value|
      prob = BNTPGFromPositiveNegativeRelations.get_node_probability_from_boolean_combination(boolean_combination, type_of_position_impact)
      prob = 1 - prob if node_value == false
      table_probabilities[node.get_table_index(node_value, boolean_combination)] = prob
      #p "pos :" + node.get_table_index(node_value, boolean_combination).to_s
      #p "Ok :" + node.get_table_index(node_value, boolean_combination).to_s if node.get_table_index(node_value, boolean_combination) > 2**node.parents.size
    }
  }
 #p table_probabilities
 table_probabilities
end