Fill missing value with the latest known element

FillMissingValues1.scala

import Double.NaN

object FillMissingValues1 extends App {
  val data = List(1.0, NaN, 2.0, NaN, NaN, 3.0, 4.0, NaN, 5.0, NaN)

  val res = data.scanLeft(0.0)( (current, item) => if (item.isNaN) current else item)

  println(res)
}

FillMissingValues2.scala

import Double.NaN

final case class Measurement(values: Seq[Double])

object FillMissingValues2 extends App {
  val data = Seq(
    Measurement(
      Seq(0.0, NaN, 2.0, 3.0, NaN, 5.0, NaN, 7.0, NaN, NaN)
    ),
    Measurement(
      Seq(100.0, 101.0, NaN, 103.0, 104.0, NaN, NaN, 107.0, 108.0, 109.0)
    ),
    Measurement(
      Seq(NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN, NaN)
    )
  )

  val zero = Measurement(values = (1 to 10).map(_ => 0.0))
  val res = data.scanLeft(zero)( (current, item) => {
    if (item.values.exists(v => v.isNaN)) {
      item.copy(values = item.values.zip(current.values).map{ case (v, current) => if (v.isNaN) current else v })
    } else {
      item
    }
  }).drop(1)

  println(res.map(m => m.values.mkString(",")).mkString("\n"))
}

output1.txt

# FillMissingValues1
List(0.0, 1.0, 1.0, 2.0, 2.0, 2.0, 3.0, 4.0, 4.0, 5.0, 5.0)

output2.txt

# FillMissingValues2
0.0,0.0,2.0,3.0,0.0,5.0,0.0,7.0,0.0,0.0
100.0,101.0,2.0,103.0,104.0,5.0,0.0,107.0,108.0,109.0
100.0,101.0,2.0,103.0,104.0,5.0,0.0,107.0,108.0,109.0