Class: PositronicBrain::Classifier::Fisher

Inherits:
Base
  • Object
show all
Defined in:
lib/positronic_brain/classifier/fisher.rb

Instance Attribute Summary

Attributes inherited from Base

#namespace, #persistence

Instance Method Summary collapse

Methods inherited from Base

#category_given_item_product, #extract_features, #initialize, #item_given_category_product, #normalized_prob_category_given_feature, #prob_category, #prob_category_given_feature, #prob_feature_given_category, #train

Methods inherited from Base

#dump_path, #initialize, initialize_persistence, #inspect, persistence, persistence_class, persistence_options

Constructor Details

This class inherits a constructor from PositronicBrain::Classifier::Base

Instance Method Details

#classify(item, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/fisher.rb', line 4

def classify(item, options={})
  best_category = options[:default] || @default_category
  best_score    = options[:minimum] || @minimum_score || 0.0

  scores = scores item

  scores.each do |category, score|
    if score > best_score
      best_category = category
      best_score    = score
    end
  end

  [best_category, best_score]
end

#fisher_score(item, category) ⇒ Object Also known as: score 



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# File 'lib/positronic_brain/classifier/fisher.rb', line 28

def fisher_score(item, category)
  prod = category_given_item_product category, item, weighted: true
  return 0.0 if prod == 0.0

  features_count = extract_features!(item).count
  Distribution::ChiSquare.q_chi2 2*features_count, -2*Math.log(prod)
end

#fisher_scores(item) ⇒ Object Also known as: scores 



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# File 'lib/positronic_brain/classifier/fisher.rb', line 20

def fisher_scores(item)
  categories.map do |category|
    score = fisher_score item, category
    [category, score]
  end
end