Merge a sequence of tuples into another sequence in scala

Question

I have a sequence of tuples like below. Number of "x" and "y"s occurred in documents "abc" and "xyz"

Seq(("abc", Map("x" -> 1, "y" -> 2)), ("xyz", Map("x" -> 2, "y" -> 1)))

How can I create an output like below from this above sequence.

Seq(("x", Map("abc" -> 1, "xyz" -> 2)), ("y", Map("abc" -> 2, "xyz" -> 1)))

you might want describe how you expect your output based on input? — prayagupadhyay
– prayagupadhyay, Commented May 18, 2018 at 0:23
Does the order of first-level keys x and y actually matter in the output? The maps in the input are not sorted. Should the output be sorted? — Andrey Tyukin
– Andrey Tyukin, Commented May 18, 2018 at 0:35

Andrey Tyukin · Accepted Answer · 2018-05-18 00:38:11Z

3

Here is one possibility:

val s = Seq(
  ("abc", Map("x" -> 1, "y" -> 2)), 
  ("xyz", Map("x" -> 2, "y" -> 1))
)

val t = (for {
  (x, yvs) <- s 
  (y, v) <- yvs
} yield (y, (x, v)))
  .groupBy(_._1)
  .mapValues(_.unzip._2.toMap)

println(t)

This produces (up to random reordering of the unsorted keys):

Map(
  x -> Map(abc -> 1, xyz -> 2),
  y -> Map(abc -> 2, xyz -> 1)
)

answered May 18, 2018 at 0:38

Andrey Tyukin

45.1k4 gold badges65 silver badges103 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Joe K Over a year ago

Was about to post pretty much the same but slightly more verbose. TIL about unzip. 👍

Collectives™ on Stack Overflow

Merge a sequence of tuples into another sequence in scala

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related