Class: RSemantic::Transform::TFIDF

Inherits:
Object
  • Object
show all
Defined in:
lib/rsemantic/transform/tf_idf_transform.rb

Constant Summary collapse

@@number_of_documents_with_term = 
[]

Class Method Summary collapse

Class Method Details

.number_of_documents_with_term(row_index, matrix) ⇒ Object 



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# File 'lib/rsemantic/transform/tf_idf_transform.rb', line 22

def self.number_of_documents_with_term(row_index, matrix)
  @@number_of_documents_with_term[row_index] ||= matrix.row(row_index).where.size
end

.transform!(matrix) ⇒ Object 



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# File 'lib/rsemantic/transform/tf_idf_transform.rb', line 6

def self.transform!(matrix)
  number_of_documents = matrix.size2
  @@number_of_documents_with_term = []

  matrix.transpose.enum_for(:each_row).with_index do |document, column_index|
    document.enum_for(:each).with_index do |term_weight, row_index|
      unless term_weight == 0.0
        inverse_document_frequency = 1 + GSL::Sf.log(number_of_documents / (number_of_documents_with_term(row_index, matrix).to_f + 1))
        term_frequency = Math.sqrt(term_weight)

        matrix[row_index, column_index] = term_frequency * inverse_document_frequency
      end
    end
  end
end