Method: Evoc::Evaluate.t_ap

Defined in:
lib/evoc/evaluate.rb

.t_ap(rec:, exp: nil) ⇒ Object

r_p : relevant items in previous groups i_p : index previous group r_g : relevant items in group n_g : items in group i : index of current item



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# File 'lib/evoc/evaluate.rb', line 205

def self.t_ap(rec:,exp: nil)
  # AP is 0 for the empty list
  if rec.is_a?(Array) && rec.empty? # array and empty
    return nil
  end
  self.validateInput(rec)

  ap = 0
  r_p = 0
  i_p = 0
  rec.each do |cluster|
    r_g = cluster.inject(&:+).to_r
    n_g = cluster.size.to_r
    cluster.each_with_index do |_,i|
      i = i_p + i + 1
      chance_relevant = r_g/n_g
      avg_previous_rel = if (n_g == 1)
                           (r_p + 1) * (1/i)
                         else
                           (r_p + (i - i_p - 1)*((r_g-1)/(n_g-1)) + 1) * (1/i)
                         end

      item_ap_contribution = chance_relevant * avg_previous_rel

      ap = ap + item_ap_contribution
    end
    r_p = r_p + r_g
    i_p = i_p + n_g
  end
  # if the number of relevant documents is not supplied
  # assume that the recommendation contains all relevant documents
  if exp.nil?
    exp = r_p
  else
    if r_p > exp
      raise ArgumentError, "Found more relevant items than the provided number of relevant items"
    end
  end
  return (r_p == 0 ? 0 : (ap/exp).to_f)
end