Class: PositronicBrain::Classifier::Base

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

Direct Known Subclasses

Fisher, NaiveBayes

Instance Attribute Summary

Attributes inherited from Base

#namespace, #persistence

Instance Method Summary collapse

Methods inherited from Base

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

Constructor Details

#initialize(namespace, options = {}, &extract_block) ⇒ Base

Returns a new instance of Base.



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# File 'lib/positronic_brain/classifier/classifier.rb', line 14

def initialize(namespace, options = {}, &extract_block)
  options = options.dup

  @assumed_probability = options.delete(:assumed_probability) || 0.5
  @default_category    = options.delete(:default_category)
  @minimum_score       = options.delete(:minimum_score)       || 0.0
  @assumed_weight      = options.delete(:assumed_weight)      || 1

  @extract_block = extract_block if block_given?

  super namespace, options
end

Instance Method Details

#category_given_item_product(category, item, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 57

def category_given_item_product(category, item, options={})
  prod  = 1.0
  extract_features!(item).each do |feature|
    prod *= normalized_prob_category_given_feature(category, feature, options)
  end
  prod
end

#classify(item, default = nil) ⇒ Object

Raises:

  • (NotImplementedError) 


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# File 'lib/positronic_brain/classifier/classifier.rb', line 31

def classify(item, default = nil)
  raise NotImplementedError
end

#extract_features(item) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 27

def extract_features(item)
  item.downcase.split(/\P{Word}+/).uniq
end

#item_given_category_product(item, category, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 49

def item_given_category_product(item, category, options={})
  prod  = 1.0
  extract_features!(item).each do |feature|
    prod *= prob_feature_given_category(feature, category, options)
  end
  prod
end

#normalized_prob_category_given_feature(category, feature, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 78

def normalized_prob_category_given_feature(category, feature, options={})
  feature_given_category       = prob_feature_given_category feature, category
  all_feature_given_categories = categories.map do |cat|
    prob_feature_given_category feature, cat
  end.sum

  if options[:weighted]
    fc = feature_count feature
    weighted feature_given_category/all_feature_given_categories, fc
  else
    return 0.0 if fc == 0.0
    feature_given_category/all_feature_given_categories
  end
end

#prob_category(category) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 42

def prob_category(category)
  tc = total_count
  return 0.0 if total_count == 0.0

  category_count(category)/tc
end

#prob_category_given_feature(category, feature, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 93

def prob_category_given_feature(category, feature, options={})
  fc                  = feature_count feature
  feature_in_category = feature_in_category_count feature, category

  if options[:weighted]
    weighted feature_in_category/fc, fc
  else
    return 0.0 if fc == 0.0
    feature_in_category/fc
  end
end

#prob_feature_given_category(feature, category, options = {}) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 65

def prob_feature_given_category(feature, category, options={})
  cc                  = category_count category
  feature_in_category = feature_in_category_count feature, category

  if options[:weighted]
    fc = feature_count feature
    weighted feature_in_category/cc, fc
  else
    return 0.0 if cc == 0.0
    feature_in_category/cc
  end
end

#train(item, category) ⇒ Object 



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# File 'lib/positronic_brain/classifier/classifier.rb', line 35

def train(item, category)
  extract_features!(item).each do |feature|
    increment_feature feature, category
  end
  increment_category category
end