Scala extract from Seq of tuples

Question

Here's a seq of tuples in Scala

val t = Seq((1,2,3),(4,5,6))

I like to extract the first element of each tuple into its own sequence, i.e.,

Seq(1,4)

How do I do this in Scala?

axel22 · Accepted Answer · 2012-06-20 15:13:12Z

11

Simply use map and transform each tuple to its first element:

t.map(x => x._1)

Or shorter:

t.map(_._1)

answered Jun 20, 2012 at 15:13

axel22

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1 Comment

Martin McNulty Over a year ago

Or, if you prefer not to use the _i accessors: t map { case (n, _, _) => n }

Amir Hossein Javan · Accepted Answer · 2017-07-01 10:11:58Z

6

The general form to extract more than one columns:

def extractColumns3[T1, T2, T3](t: Seq[(T1, T2, T3)]): (Seq[T1],   Seq[T2], Seq[T3]) =
t.foldLeft((Seq.empty[T1], Seq.empty[T2], Seq.empty[T3])) { (columns, row) ⇒
  (columns._1 :+ row._1, columns._2 :+ row._2, columns._3 :+ row._3)
}

answered Jul 1, 2017 at 10:11

Amir Hossein Javan

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1 Comment

Amir Hossein Javan Over a year ago

This solution has better performance for extracting more than one columns

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