centerWeightedAverage.scala

// Compute center-weighted moving average of equally spaced values, some of which may be None
// period should be odd
def centerWeightedAverage (values: Iterable[Option[Double]], period: Int): Seq[Option[Double]] = {
  // prepend and append period/2 Nones
  val valuesWithBuffers = List.fill(period / 2)(None) ++ values ++ List.fill(period / 2)(None)
  valuesWithBuffers
    .sliding(period)
    .map(_.flatten)
    .map(x => if (x.size > 0) Some(x.sum.toDouble / x.size) else None)
    .take(values.size)
    .toList
}