alternate way to proceed without list in scala

I have a scala code like this

 def avgCalc(buffer: Iterable[Array[String]], list: Array[String]) = {
    val currentTimeStamp = list(1).toLong // loads the timestamp column
    var sum = 0.0
    var count = 0
    var check = false
    import scala.util.control.Breaks._
    breakable {
      for (array <- buffer) {
        val toCheckTimeStamp = array(1).toLong // timestamp column
        if (((currentTimeStamp - 10L) <= toCheckTimeStamp) && (currentTimeStamp >= toCheckTimeStamp)) { // to check the timestamp for 10 seconds difference
          sum += array(5).toDouble // RSSI weightage values
          count += 1
        }

        if ((currentTimeStamp - 10L) > toCheckTimeStamp) {

          check = true
          break

        }
      }
    }
     list :+ sum

  }

I will call the above function like this

 import spark.implicits._
  val averageDF =
    filterop.rdd.map(_.mkString(",")).map(line => line.split(",").map(_.trim))
      .sortBy(array => array(1), false) // Sort by timestamp
      .groupBy(array => (array(0), array(2))) // group by tag and listner
      .mapValues(buffer => {
        buffer.map(list => {
         avgCalc(buffer, list) // calling the average function 
        })
      })
      .flatMap(x => x._2)
      .map(x => findingavg(x(0).toString, x(1).toString.toLong, x(2).toString, x(3).toString, x(4).toString, x(5).toString.toDouble, x(6).toString.toDouble)) // defining the schema through case class
      .toDF // converting to data frame

The above code is working fine.But I need to get rid of list.My senior ask me to remove the list,Because list reduces the execution speed.Any suggestions to proceed without list ? Any help will be appreciated.