Class: FeatureSet::FeatureBuilder::WordVector

Inherits:
Base
  • Object
show all
Defined in:
lib/feature_set/feature_builder/word_vector.rb

Instance Attribute Summary collapse

Attributes inherited from Base

#options

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ WordVector

Returns a new instance of WordVector.



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# File 'lib/feature_set/feature_builder/word_vector.rb', line 8

def initialize(options = {})
  super
end

Instance Attribute Details

#idfs ⇒ Object

Returns the value of attribute idfs.



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# File 'lib/feature_set/feature_builder/word_vector.rb', line 6

def idfs
  @idfs
end

Instance Method Details

#before_generate_features(dataset) ⇒ Object 



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# File 'lib/feature_set/feature_builder/word_vector.rb', line 12

def before_generate_features(dataset)
  @idfs = {}
  dataset.each do |row|
    row.each do |key, datum|
      next if key == :class
      if datum.value.is_a?(String)
        idfs[key] ||= {}
        datum.token_counts.keys.each do |token|
          idfs[key][token] ||= 0
          idfs[key][token] += 1
        end
      end
    end
  end

  num_docs = dataset.length
  idfs.each do |feature, freqs|
    freqs.each do |key, value|
      idfs[feature][key] = Math.log(num_docs / value.to_f)
    end
  end
  
  def generate_features(datum, key, row)
    return {} unless datum.value.is_a?(String)
    num_words = datum.tokens.length.to_f
    idfs[key].inject({}) do |memo, (word, idf)|
      memo[word] = ((datum.token_counts[word] || 0) / num_words) * idf
      memo
    end
  end
end

#generate_features(datum, key, row) ⇒ Object 



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# File 'lib/feature_set/feature_builder/word_vector.rb', line 34

def generate_features(datum, key, row)
  return {} unless datum.value.is_a?(String)
  num_words = datum.tokens.length.to_f
  idfs[key].inject({}) do |memo, (word, idf)|
    memo[word] = ((datum.token_counts[word] || 0) / num_words) * idf
    memo
  end
end