keyBy

Create a Pair RDD, forming one pair for each item in the original RDD. The pair's key is calculated from the value via a user-supplied function.

Let us look at the legend and overview of the visual RDD Api.

val x = sc.parallelize(Array("John", "Fred", "Anna", "James"))
val y = x.keyBy(w => w.charAt(0))

println(y.collect().mkString(", "))