scala - value mkString is not a value of org.apache.spark.rdd.RDD[Int] -


i changed line: 

val ratednum = rows.sortby(- _._2).map{case (user , ratednum) => ratednum}.take(20).mkstring("::")

to:

val ratednum = rows.sortby(- _._2).map{case (user , ratednum) => ratednum}.mkstring("::")

but eclipse giving me error hint: value mkstring not value of org.apache.spark.rdd.rdd[int]

what error mean?

val ratednum = rows.sortby(- _._2).map{case (user , ratednum) => ratednum}

this returns org.apache.spark.rdd.rdd[int] not gentraversableonce. although has lot of methods defined makes scala collection of int, it not (abstract class rdd[t] extends serializable logging). it's bit promise of collection int. have poll collection out before mkstring results.

call .collect() on rdd[int] before perform mkstring.

val ratednum = rows.sortby(- _._2).map{case (user , ratednum) => ratednum}.collect.mkstring("::")

or can add implicit conversion:

implicit def toarray[t](rdd: rdd[t]) = rdd.collect()

-

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