Class: NLPBackpack::Classifier::NaiveBayes

Inherits:
Base
  • Object
show all
Defined in:
lib/nlp_backpack/classifier/naive_bayes.rb

Instance Attribute Summary

Attributes inherited from Base

#db_filepath

Instance Method Summary collapse

Methods inherited from Base

load, #save

Constructor Details

#initialize(*klasses) ⇒ NaiveBayes

Returns a new instance of NaiveBayes.



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# File 'lib/nlp_backpack/classifier/naive_bayes.rb', line 20

def initialize(*klasses)
  @features_count = {}
  @klass_count = {}
  @klasses = klasses

  klasses.each do |klass|
    @features_count[klass] = Hash.new(0.0)
    @klass_count[klass] = 0.0
  end
end

Instance Method Details

#classify(*features) ⇒ Object

P(Class | Item) = P(Item | Class) * P(Class)



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# File 'lib/nlp_backpack/classifier/naive_bayes.rb', line 39

def classify(*features)
  scores = {}
  @klasses.each do |klass|
    scores[klass] = (prob_of_item_given_a_class(features, klass) * prob_of_class(klass))
  end
  scores.sort {|a,b| b[1] <=> a[1]}[0]
end

#train(klass, *features) ⇒ Object 



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# File 'lib/nlp_backpack/classifier/naive_bayes.rb', line 31

def train(klass, *features)
  features.uniq.each do |feature|
    @features_count[klass][feature] += 1
  end
  @klass_count[klass] += 1
end