accumulate and normalise

  def accumulate(arr: Array[Array[Double]]): Array[Array[Double]] = {
    def accumulateRows(arr: List[Array[Double]], result: ListBuffer[Array[Double]]): Array[Array[Double]] = arr match {
      case Nil => result.toArray
      case (x :: xs) => accumulateRows(xs, result += x.scanLeft(if (result.length > 0) result.last.last else 0.0)(_ + _).drop(1))
    }
    accumulateRows(arr.toList, new ListBuffer[Array[Double]]())
  }

  def accumulateAndNormalise(arr: Array[Array[Double]]): Array[Array[Double]] = {
    val result = accumulate(arr)
    result.map(_.map(_/result.last.last))
  }