Example of using partial functions in collect doing filtering and mapping in one interation over a sequence.

partial.scala

val wordFrequencies = ("habitaul", 6) :: ("and", 56) :: ("consuetudinary", 2) :: ("additionally", 27) :: ("homely", 5) :: ("society", 13) :: Nil

//verbose implementation - two iterations one for filter and one for map
def wordsWithoutOutliers(wordFrequencies: Seq[(String, Int)]): Seq[String] =
  wordFrequencies.filter{case (w, f) => f > 3 && f <25}.map{ case (w,f) => w }

//defining partial function using anonymous function pattern matching
val pf: PartialFunction[(String, Int), String] = {
 case (word, freq) if freq > 3 && freq < 25 => word
}
  
wordFrequencies.collect(pf)
wordFrequencies.collect{case (word, freq) if freq > 3 && freq < 25 => word} //same as above