timePartition.scala

def timePartition (
    data: DataFrame,
    timeCol : String,
    outputCol : String,
    startTime : Long = 1404198000000L
  ) : DataFrame = {
    val addTime : Long = 604800000L // Discretize time into weeks.
    val udf : UserDefinedFunction = functions.udf(
      (t : Timestamp) => ((t.getTime - startTime) / addTime).toInt
    )
    
    data.withColumn(outputCol, udf(data(timeCol)))
    
  }