Adding mean and variance to Scala collections.

TraversableWithStatistics.scala

object TraversableWithStatistics {

  implicit class RichTraversable[A](collection: Traversable[A])(implicit val numeric : Numeric[A]) {

    private def pow2[C](x: C)(implicit num: Numeric[C]) = math.pow(num.toDouble(x), 2)

    private def sqrt[C](x: C)(implicit num: Numeric[C]) = math.sqrt(num.toDouble(x))

    def mean = {
      numeric.toDouble(collection.sum) / collection.size
    }

    def variance = {
      val me: Double = mean
      implicit val doubleNum = implicitly[Numeric[Double]]
      collection.map(x => pow2(numeric.toDouble(x) - me)).sum / collection.size
    }

    def stddev = sqrt(variance)
  }

}