Scala Map Word Count? - scala

Question

This problem appeared under "Maps and Tuples" Chapter in Scala for the Impatient
Write a program that reads words from a file. Use a mutable map to count how often each word appears.
My attempt is
// source file: https://www.gutenberg.org/cache/epub/35709/pg35709.txt
scala> val words = scala.io.Source.fromFile("pg35709.txt").mkString.split("\\s+")
words: Array[String] = Array(The, Project, Gutenberg, EBook, of, Making, Your, Camera, Pay,, by, Frederick, C., Davis,
This, eBook, is, for, the, use, of, anyone, anywhere, at, no, cost, and, with, almost, no, restrictions, whatsoever.,
You, may, copy, it,, give, it, away, or, re-use, it, under, the, terms, of, the, Project, Gutenberg, License, included,
with, this, eBook, or, online, at, www.gutenberg.net, Title:, Making, Your, Camera, Pay, Author:, Frederick, C., Davis,
Release, Date:, March, 29,, 2011, [EBook, #35709], Language:, English, ***, START, OF, THIS, PROJECT, GUTENBERG, EBOOK,
MAKING, YOUR, CAMERA, PAY, ***, Produced, by, The, Online, Distributed, Proofreading, Team, at, http://www.pgdp.net,
(This, file, was, produced, from, images, generously, made, available, by, The, In...
scala> val wordCount = scala.collection.mutable.HashMap[String, Int]()
wordCount: scala.collection.mutable.HashMap[String,Int] = Map()
scala> for (word <- words) {
| val count = wordCount.getOrElse(word, 0)
| wordCount(word) = count + 1
| }
scala> word
wordCount words
scala> wordCount
res1: scala.collection.mutable.HashMap[String,Int] = Map(arts -> 1, follow -> 3, request, -> 1, Lines. -> 1,
demand -> 7, 1.E.4. -> 1, PRODUCT -> 2, 470 -> 1, Chicago, -> 3, scenic -> 1, J2 -> 1, untrimmed -> 1,
photographs--not -> 1, basis. -> 1, "prints -> 1, instances. -> 1, Onion-Planter -> 1, trick -> 1,
illustrating -> 3, prefer. -> 1, detected -> 1, non-exclusive. -> 1, famous -> 1, Competition -> 2,
expense -> 1, created -> 2, renamed. -> 1, maggot -> 1, calendar-photographs, -> 1, widely-read -> 1,
Publisher, -> 1, producers -> 1, Shapes -> 1, ARTICLES -> 2, yearly -> 2, retoucher -> 1, satisfy -> 2,
agrees: -> 1, Gentleman_, -> 1, intellectual -> 2, hard -> 2, Porch. -> 1, sold.) -> 1, START -> 1, House -> 2,
welcome -> 1, Dealers' -> 1, ... -> 2, pasted -> 1, _Cosmopolitan_ -...
While I know that this works, I wanted to know if there is Scalaesque way of achieving the same

Answer 1

You can do this:
val wordCount = words.groupBy(w => w).mapValues(_.size)
The groupBy method returns a map from the result of the given function, to a collection of values that return the same value from the function. In this case, a Map[String, Array[String]]. Then mapValues maps the Array[String] to their lengths.

Answer 2

If by Scalaesque way of achieving the same, you mean with using a mutable Map, here is a version:
scala> val data = Array("The", "Project", "Gutenberg", "EBook", "of", "Making", "Your", "The")
data: Array[String] = Array(The, Project, Gutenberg, EBook, of, Making, Your, The)
scala> val wordCount = scala.collection.mutable.HashMap[String, Int]().withDefaultValue(0)
wordCount: scala.collection.mutable.Map[String,Int] = Map()
scala> data.foreach(word => wordCount(word) += 1 )
scala> wordCount
res6: scala.collection.mutable.Map[String,Int] = Map(Making -> 1, of -> 1, Your -> 1, Project -> 1, Gutenberg -> 1, EBook -> 1, The -> 2)

Answer 3

author wanted to get it done in the mutable way in this chapter, so here is my mutable solution (in scala way it should be less verbouse)
var wordsMap = new scala.collection.mutable.HashMap[String, Int]
val in = new Scanner(new java.io.File("/home/artemvlasenko/Desktop/myfile.txt"))
while (in.hasNext) {
val word = in.next()
val count = wordsMap.getOrElse(word, 0)
wordsMap(word) = count + 1
in.next()
}
println(wordsMap.mkString(", "))