class Airbrake::TDigest

def p_rank(x)
  is_array = x.is_a? Array
  x = [x] unless is_array
  min = @centroids.first
  max = @centroids.last
  x.map! do |item|
    if size == 0
      nil
    elsif item < min[1].mean
      0.0
    elsif item > max[1].mean
      1.0
    else
      _cumulate(true)
      bound = bound_mean(item)
      lower, upper = bound
      mean_cumn = lower.mean_cumn
      if lower != upper
        mean_cumn += (item - lower.mean) * (upper.mean_cumn - lower.mean_cumn) \
          / (upper.mean - lower.mean)
      end
      mean_cumn / @size
    end
  end
  is_array ? x : x.first
end