TemperatureActor.scala

  def daily(day: Day, requester: ActorRef): Unit =
    sc.cassandraTable[Double](keyspace, rawtable)
      .select("temperature").where("wsid = ? AND year = ? AND month = ? AND day = ?",
        day.wsid, day.year, day.month, day.day)
      .collectAsync()
      .map(toDaily(_, day)) pipeTo requester
  
  private def toDaily(aggregate: Seq[Double], key: Day): WeatherAggregate =
    if (aggregate.nonEmpty) {
      val data = toDailyTemperature(key, StatCounter(aggregate))
      self ! data
      data
    } else NoDataAvailable(key.wsid, key.year, classOf[DailyTemperature]) // not wanting to return an option to requester

  private def toDailyTemperature(key: Day, stats: StatCounter): DailyTemperature =
    DailyTemperature(key.wsid, key.year, key.month, key.day,
      high = stats.max, low = stats.min, mean = stats.mean,
      variance = stats.variance, stdev = stats.stdev)