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我的要求是找到RDD中每個組的最大值。如何將定製函數傳遞給scala中的RDD的reduceByKey
我試過了下面;
scala> val x = sc.parallelize(Array(Array("A",3), Array("B",5), Array("A",6)))
x: org.apache.spark.rdd.RDD[Array[Any]] = ParallelCollectionRDD[0] at parallelize at <console>:27
scala> x.collect
res0: Array[Array[Any]] = Array(Array(A, 3), Array(B, 5), Array(A, 6))
scala> x.filter(math.max(_,_))
<console>:30: error: wrong number of parameters; expected = 1
x.filter(math.max(_,_))
^
我也嘗試了下面; 選項1:
scala> x.filter((x: Int, y: Int) => { math.max(x,y)})
<console>:30: error: type mismatch;
found : (Int, Int) => Int
required: Array[Any] => Boolean
x.filter((x: Int, y: Int) => { math.max(x,y)})
選項2:
scala> val myMaxFunc = (x: Int, y: Int) => { math.max(x,y)}
myMaxFunc: (Int, Int) => Int = <function2>
scala> myMaxFunc(56,12)
res10: Int = 56
scala> x.filter(myMaxFunc(_,_))
<console>:32: error: wrong number of parameters; expected = 1
x.filter(myMaxFunc(_,_))
如何得到這個權利?
哪裏是reduceByKey在你的代碼?爲何使用過濾器? – stholzm