How to return the last element of RDD[List[(Int,Double)]] ?

[lk]

Hi, I have the following code :

import org.apache.spark.SparkContext
import org.apache.spark.SparkContext._
import org.apache.spark.SparkConf
import math.ceil
import org.apache.spark.rdd.RDD

object test{
  def main(args: Array[String]) {
    //settings
    val sc = new SparkContext("local", "SparkTest")
   
    val NumIter:Int = 2
   
    //given list
    var mlist = List[(Int,Double)]()
   
    mlist ++= List((1, 5.0))
    mlist ++= List((2, 2.0))
    mlist ++= List((3, 3.0))
    mlist ++= List((4, 6.0))
   
    //given list to rdd
    var mlistrdd = sc.parallelize(mlist)
   
    //storing important pairs list
    var sipairs = List[List[(Int,Double)]]()
   
    //storing important pairs list to rdd
    var slist = sc.parallelize(sipairs)
   
    //store the initial values of the given list
    slist ++= storetPairs(mlistrdd)
   
    for(i <- 1 to NumIter){
        mlistrdd =  mlistrdd.map({case (x,y) => mapping(x,y)})
                    .reduceByKey((a,b) => (a+b))
       
        slist ++= storetPairs(mlistrdd)
    }
   
    //println("Stored Pairs")
    slist.foreach(println)
   
    System.exit(0)
  }
 
  def storetPairs(xs: RDD[(Int,Double)]): RDD[List[(Int,Double)]] =  {
          val out = xs.flatMap{
              var t = List[(Int,Double)]();
              x => {  t ++= List(x)  }
             
              List(t)
          }
         
          //how to return only the final element ??? (I would like this to be in the RDD if possible)
          out
      }
     
  def mapping(xx: Int,b: Double):(Int, Double) = {
    var a  = ceil(xx/2.0).toInt
    (a, b)
  }

}

The output that I receive is the following (and is stored in the "slist" variable) :
-------------------------------------------------------
List((1,5.0))
List((1,5.0), (2,2.0))
List((1,5.0), (2,2.0), (3,3.0))
List((1,5.0), (2,2.0), (3,3.0), (4,6.0))

List((1,7.0))
List((1,7.0, (2,9.0))

List((1,16.0))
-------------------------------------------------------

Instead I would like to receive :
-------------------------------------------------------
List((1,5.0), (2,2.0), (3,3.0), (4,6.0))

List((1,7.0, (2,9.0))

List((1,16.0))
-------------------------------------------------------

How is it possible in the "storetPairs" function to return only the last element of the  RDD[List[(Int,Double)]] "out" value ?
(by returning the last element I will be able to receive the desired output)

Thanks.