Scala how can I count the number of occurrences in a list
val list = List(1,2,4,2,4,7,3,2,4)
I want to implement it like this: list.count(2) (returns 3).
Answer
A somewhat cleaner version of one of the other answers is:
val s = Seq("apple", "oranges", "apple", "banana", "apple", "oranges", "oranges")
s.groupBy(identity).mapValues(_.size)
giving a Map with a count for each item in the original sequence:
Map(banana -> 1, oranges -> 3, apple -> 3)
The question asks how to find the count of a specific item. With this approach, the solution would require mapping the desired element to its count value as follows:
s.groupBy(identity).mapValues(_.size)("apple")