# File lib/gruff/line.rb, line 118
  def contains_one_point_only?(data_row)
    # Spin through data to determine if there is just one_value present.
    one_point = false
    data_row[DATA_VALUES_INDEX].each do |data_point|
      if !data_point.nil?
        if one_point
          # more than one point, bail
          return false
        else
          # there is at least one data point
          return true
        end
      end
    end
    return one_point
  end