Class: OmniCat::Classifiers::Bayes

Inherits:
Base
  • Object
show all
Defined in:
lib/omnicat/classifiers/bayes.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods inherited from Base

#add_categories, #classify_batch, #train_batch

Methods inherited from Base

#to_hash

Constructor Details

#initialize(bayes_hash = {}) ⇒ Bayes

Returns a new instance of Bayes.



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# File 'lib/omnicat/classifiers/bayes.rb', line 12

def initialize(bayes_hash = {})
  self.categories = ::OmniCat::Hash.new
  if bayes_hash.has_key?(:categories)
    bayes_hash[:categories].each do |name, category|
      self.categories[name] = ::OmniCat::Classifiers::BayesInternals::Category.new(category)
    end
  end
  self.category_count = bayes_hash[:category_count].to_i
  self.doc_count = bayes_hash[:doc_count].to_i
  self.k_value = bayes_hash[:k_value] || 1.0
  self.token_count = bayes_hash[:token_count].to_i
  self.uniq_token_count = bayes_hash[:uniq_token_count].to_i
end

Instance Attribute Details

#categories ⇒ Object

::OmniCat::Hash - Hash of categories



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# File 'lib/omnicat/classifiers/bayes.rb', line 5

def categories
  @categories
end

#category_count ⇒ Object

Integer - Total category count



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# File 'lib/omnicat/classifiers/bayes.rb', line 6

def category_count
  @category_count
end

#doc_count ⇒ Object

Integer - Total token count



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# File 'lib/omnicat/classifiers/bayes.rb', line 7

def doc_count
  @doc_count
end

#k_value ⇒ Object

Integer - Helper value for skipping some Bayes algorithm errors



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# File 'lib/omnicat/classifiers/bayes.rb', line 10

def k_value
  @k_value
end

#token_count ⇒ Object

Integer - Total token count



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# File 'lib/omnicat/classifiers/bayes.rb', line 8

def token_count
  @token_count
end

#uniq_token_count ⇒ Object

Integer - Total uniq token count



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# File 'lib/omnicat/classifiers/bayes.rb', line 9

def uniq_token_count
  @uniq_token_count
end

Instance Method Details

#add_category(name) ⇒ Object

Allows adding new classification category

Parameters

  • name - Name for category

Examples

# Create a classification category
bayes = Bayes.new
bayes.add_category("positive")



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# File 'lib/omnicat/classifiers/bayes.rb', line 37

def add_category(name)
  if category_exists?(name)
    raise StandardError,
          "Category with name '#{name}' is already exists!"
  else
    self.category_count +=1
    self.categories[name] = ::OmniCat::Classifiers::BayesInternals::Category.new
  end
end

#classify(doc) ⇒ Object

Classify the given document

Parameters

  • doc - The document for classification

Returns

  • result - OmniCat::Result object

Examples

# Classify a document
bayes.classify("good documentation")
=>



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# File 'lib/omnicat/classifiers/bayes.rb', line 90

def classify(doc)
  if category_count < 2
    return raise StandardError,
                 "At least 2 categories needed for classification process!"
  end
  score = -1000000
  result = ::OmniCat::Result.new
  self.categories.each do |category_name, category|
    result.scores[category_name] = doc_probability(category, doc)
    if result.scores[category_name] > score
      result.category[:name] = category_name
      score = result.scores[category_name]
    end
    result.total_score += result.scores[category_name]
  end
  result.total_score = 1 if result.total_score == 0
  result.category[:percentage] = (
    result.scores[result.category[:name]] * 100.0 /
    result.total_score
  ).floor
  result
end

#train(category_name, doc) ⇒ Object

Train the desired category with a document

Parameters

  • category - Name of the category from added categories list

  • doc - Document text

Examples

# Train the desired category
bayes.train("positive", "clear documentation")
bayes.train("positive", "good, very well")
bayes.train("negative", "bad dog")
bayes.train("neutral", "how is the management gui")



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# File 'lib/omnicat/classifiers/bayes.rb', line 61

def train(category_name, doc)
  if category_exists?(category_name)
    increment_doc_counts(category_name)
    update_priors
    doc.tokenize_with_counts.each do |token, count|
      increment_token_counts(category_name, token, count)
      self.categories[category_name].tokens[token] = self.categories[category_name].tokens[token].to_i + count
    end
  else
    raise StandardError,
          "Category with name '#{category_name}' does not exist!"
  end
end