code: def percentage(**options)
        if nan? || zero?
          number_to_percentage 0, **options
        elsif infinite?
          # TODO: Return nil, or lookup an optional representation in I18n?
          nil
        elsif positive?
          number_to_percentage relative, format: '+%n%', **options
        else
          number_to_percentage relative, **options
        end
      end
docs: Returns Comparator#relative formatted as a percentage.
  
   If the relative percentage evaluates to Infinity or -Infinity, +nil+ is
   returned. If it evaluates to NaN, 0 is returned.