Hello ! I 'm rookie to spark scala, here is my problem : tk's in advance for your help
 my input dataframe looks like this :
index bucket time ap station rssi
 0 1 00:00 1 1 -84.0
 1 1 00:00 1 3 -67.0
 2 1 00:00 1 4 -82.0
 3 1 00:00 1 2 -68.0
 4 1 00:00 2 5 -68.0
 5 2 00:15 1 3 -83.0
 6 2 00:15 1 2 -82.0
 7 2 00:15 1 4 -80.0
 8 2 00:15 1 1 -72.0
 9 2 00:15 2 5 -72.0
 10 3 00:30 1 4 -85.0
 11 3 00:30 1 3 -77.0
 12 3 00:30 1 2 -70.0
 13 3 00:30 2 5 -70.0
 I would like to write an algorithm to do this : 
 for each ap 
  for each station 
     for each bucket 
        if rssi(previous bucket)<rssi(bucket)
        print message
 i don't know how to do this in scala ...
 my start is :
object coveralg {
    def main(args:Array[String]){
        val spark =SparkSession.builder().appName("coveralg").getOrCreate()
        import spark.implicits._
            val input_data =  spark.read.format("csv").option("header","true").load(args(0))
    }
}
    but i don't know how to implement a loop over a dataframe and select values to do the if
    Thank you for your answer