Grouping method examples for Scala Vector and Seq

This page shows a few examples of “grouping” methods that can be used on the Scala Vector. Note that these same methods will also work with a Scala Seq, including IndexedSeq.

Grouping methods

Method Returns
groupBy(f) A map of collections created by the function f
grouped Breaks the vector into fixed-size iterable collections
partition(p) Two collections created by the predicate p
sliding(i,s) Group elements into fixed size blocks by passing a sliding window of size i and step s over them
span(p) A collection of two collections; the first created by vector.takeWhile(p), and the second created by vector.dropWhile(p)
splitAt(i) A collection of two collections by splitting the vector at index i
unzip The opposite of zip, breaks a collection into two collections by dividing each element into two pieces; such as breaking up a vector of Tuple2 elements

Examples

val firstTen = (1 to 10).toVector      # Vector(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)

firstTen.groupBy(_ > 5)                # Map(false -> Vector(1, 2, 3, 4, 5), true -> Vector(6, 7, 8, 9, 10))
firstTen.grouped(2)                    # Iterator[Vector[Int]] = non-empty iterator
firstTen.grouped(2).toVector           # Vector(Vector(1, 2), Vector(3, 4), Vector(5, 6), Vector(7, 8), Vector(9, 10))
firstTen.grouped(5).toVector           # Vector(Vector(1, 2, 3, 4, 5), Vector(6, 7, 8, 9, 10))

"foo bar baz".partition(_ < 'c')       # (" ba ba", foorz)  // a Tuple2
firstTen.partition(_ > 5)              # (Vector(6, 7, 8, 9, 10), Vector(1, 2, 3, 4, 5))

firstTen.sliding(2)                    # Iterator[Vector[Int]] = non-empty iterator
firstTen.sliding(2).toVector           # Vector(Vector(1, 2), Vector(2, 3), Vector(3, 4), Vector(4, 5), Vector(5, 6), Vector(6, 7), Vector(7, 8), Vector(8, 9), Vector(9, 10))  
firstTen.sliding(2,2).toVector         # Vector(Vector(1, 2), Vector(3, 4), Vector(5, 6), Vector(7, 8), Vector(9, 10))  
firstTen.sliding(2,3).toVector         # Vector(Vector(1, 2), Vector(4, 5), Vector(7, 8), Vector(10))
firstTen.sliding(2,4).toVector         # Vector(Vector(1, 2), Vector(5, 6), Vector(9, 10)) 

val x = Vector(15, 10, 5, 8, 20, 12)
x.groupBy(_ > 10)                      # Map(false -> Vector(10, 5, 8), true -> Vector(15, 20, 12))
x.partition(_ > 10)                    # (Vector(15, 20, 12), Vector(10, 5, 8))
x.span(_ < 20)                         # (Vector(15, 10, 5, 8), Vector(20, 12))
x.splitAt(2)                           # (Vector(15, 10), Vector(5, 8, 20, 12))

More information:

More on the Scala Vector

I created this tutorial to show examples of grouping methods on Scala Vector or Seq, but for many more examples of how to work with Vector, see my Scala Vector class syntax and method examples tutorial.

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