CODEWITHSUNDEEP
scala
Alan C.
Alan C.

Reputation: 635

Converting Map[String, Seq[Int]] to Seq[Seq[Int]]

I am trying to convert data that looks like this:

val inputData =
  Seq(("STUDY1", "Follow-up", 1),
    ("STUDY1", "Off Study", 2),
    ("STUDY1", "Screening", 3),
    ("STUDY1", "Treatment", 4),
    ("STUDY2", "Follow-up", 5),
    ("STUDY2", "Off Study", 6),
    ("STUDY2", "Screening", 7),
    ("STUDY2", "Treatment", 8));

into data that looks like this:

val desiredData =
  Seq(Seq(1,2,3,4),
    Seq(5,6,7,8));

The closest that I've gotten is with this:

val result: Map[String, Seq[Int]] =
  data.groupBy(i => i._1)
    .mapValues(j => j.map(k => k._3))
    .mapValues(_.toArray)

result.values.toSeq

This yields:

res0: Seq[Seq[Int]] = Stream(WrappedArray(1, 2, 3, 4), ?)

That last question mark is throwing me for a loop.

EDIT Future internet travelers who land here: my code actually did work ... my confusion stemmed from understanding what the ? was all about. Answers from folks down below helped me see that mapValues did lazy evaluation, and that the ? simply implies that.

Upvotes: 2

Views: 1121

Answers (2)

gzm0
gzm0

Reputation: 14842

mapValues on Map is lazy (unlike any other method on a default Map). So that might be the issue there. Have you tried:

data.groupBy(_._1).map(_._2.map(_._3).toArray)

Note that the toArray is completely optional here.

Upvotes: 6

Luong Ba Linh
Luong Ba Linh

Reputation: 802

val result: List[Seq[Int]] =
  data.groupBy(_._1).mapValues(_.map(_._3)).values.toList

Upvotes: 3

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