ts1.scala

case class FeaturesRecord(key: String, ts:Timestamp, 
      features: Seq[Float], label: Float)
  
private def getFeaturesDataFrame(df: DataFrame): Try[Dataset[FeaturesRecord]] = Try {
    df.map(row => {
      val key = row.getAs[String]("app_id")
      val label = row.getAs[Int]("installs").toFloat
      val ts = row.getAs[Timestamp]("event_hour")
      val dayOfWeek = row.getAs[Int]("day_of_week").toFloat
      val hourOfDay = row.getAs[Int]("hour_of_day").toFloat
      var features = Seq(dayOfWeek, hourOfDay) ++
        (1 to (6)).map(index => row.getAs[Int](s"lag${index}").toFloat)

      (key, ts, features, label)
    }).toDF("key", "ts", "features", "label")
      .as[FeaturesRecord]
  }