stats_helper.rb

class Array
  def average
    self.sum / self.size.to_f
  end

  def sum
    self.reduce(0) { |l, r| l + r }
  end

  # TODO: check
  def std_deviation
    center = self.average
    self.reduce(0) { |base, v| base += v - center }
  end

  def chartifize
    values = self.map(&:attributes)
    chart = {}
    values.first&.keys&.each { |k| chart[k] = [] }
    values.each { |line| line.each { |k, v| chart[k] << v } }
    chart
  end
end