value toDF is not a member of org.apache.spark.rdd.RDD

idea顯示toDF() 沒有這個函數，顯示錯誤:

Error:(82, 8) value toDF is not a member of org.apache.spark.rdd.RDD[com.didichuxing.scala.BaseIndex]
possible cause: maybe a semicolon is missing before `value toDF'?
    }).toDF()

解決：
增加一行：

import sqlContext.implicits._

http://ifeve.com/spark-sql-dataframes/

在spark1.3，從RDD到DataFrame的隱式轉換隔離出來，單獨放到SQLContext.implicits對象中，所以現在需要把RDD轉換為Dataframe就需要引入這個