how to make sum of a column in a list in scala-CodePudding

I am a quite new in scala and trying to learn especially collections. I couldn't find a way to sum of the second column by group bying the first one. My data is as follows:

val a2 = List(("Comedy",2.0),
  ("Comedy",2.5),
  ("Adv",3.0),
  ("Adv",2.5)

My aim is to use group by 1st sum the 2nd one:

Comedy, 4.5
Adv, 5.5

I did group by but .sum(i => i._2) didn't work. Do you know the way to do that?

CodePudding user response：

You can use groupBy before sum:

  List(
    ("Comedy", 2.0),
    ("Comedy", 2.5),
    ("Adv", 3.0),
    ("Adv", 2.5)
  )
    .groupBy(_._1)
    .map(group => (group._1, group._2.map(_._2).sum))
    .foreach(println)