What is the correct way to get a subarray in Scala?

Question

I am trying to get a subarray in scala, and I am a little confused on what the proper way of doing it is. What I would like the most would be something like how you can do

Answer 1

An example of extracting specific columns from a 2D Scala Array (original_array):

import scala.collection.mutable.ArrayBuffer

val sub_array = ArrayBuffer[Array[String]]()
val columns_subset: Seq[String] = Seq("ColumnA", "ColumnB", "ColumnC")
val columns_original = original_array(0)

for (column_now <- columns_subset) {
      sub_array += original_array.map{_(columns_original.indexOf(column_now))}
    }
sub_array

Answer 2

You can call the slice method:

scala> Array("foo", "hoo", "goo", "ioo", "joo").slice(1, 4)
res6: Array[java.lang.String] = Array(hoo, goo, ioo)

It works like in python.

Answer 3

Imagine you have an array with elements from a to f

scala> val array = ('a' to 'f').toArray // Array('a','b','c','d','e','f')

Then you can extract a sub-array from it in different ways:

1. Dropping the first n first elements with drop(n: Int)

   array.drop(2) // Array('c','d','e','f')

2. Take the first n elements with take(n: Int)

   array.take(4) // Array('a','b','c','d')

3. Select any interval of elements with slice(from: Int, until: Int). Note that until is excluded.

   array.slice(2,4) // Array('c','d')

   The slice method is stricly equivalent to:
   array.take(4).drop(2) // Array('c','d')

4. Exclude the last n elements with dropRight(n: Int):

   array.dropRight(4) // Array('a','b')

5. Select the last n elements with takeRight(n: Int):

   array.takeRight(4) // Array('c','d','e','f')

Reference: Official documentation