def update(time, *data)
      new_data = data.map {|item| item.nil? ? "U" : item}
      new_data = [time.to_i] + new_data
      
      Wrapper.update(rrd_file, new_data.join(":"))
    end
def update(time, *data)
      new_data = data.map {|item| item.nil? ? "U" : item}
      new_data = [time.to_i] + new_data
      
      Wrapper.update(rrd_file, new_data.join(":"))
    end
Basic usage: rrd.update Time.now, 20.0, 20, nil, 2

 Note: All datasources must receive a value, based on datasources order in rrd file