table.scala

object Sample {

  def main(args: Array[String]): Unit = {

    val x = Seq(
      Seq("F", "F", "M", "M", "M") map ("SEX" -> _),
      Seq(158, 162, 177, 173, 166) map ("HEIGHT" -> _),
      Seq(51D, 55D, 72D, 57D, 64D) map ("WEIGHT" -> _)
    ).transpose

    val heights = x flatMap (_ collect { case ("HEIGHT", n) => n })
    println(heights) // List(158, 162, 177, 173, 166)

    val mean = {
      val weights = x flatMap (_ collect { case ("WEIGHT", n: Double) => n })
      weights.sum / weights.length
    }
    println(mean) // 59.8

    val seconds = x collect { case _ :+ ((_, n: Int)) :+ _ => n }
    println(seconds) // List(158, 162, 177, 173, 166)

    val line0 = x(0)
    println(line0) // List((SEX,F), (HEIGHT,158), (WEIGHT,51.0))

    val height0 = line0 collectFirst { case ("HEIGHT", n) => n }
    println(height0) // Some(158)
  }
}

rf. http://cse.naro.affrc.go.jp/takezawa/r-tips/r/39.html