我试图在scala中减去两列RDD3tuples。然而，当我试图在代码中减去r-a时，我得到了这个错误：

overloaded method value - with alternatives:
[error]   (x: Double)Double <and>
[error]   (x: Float)Double <and>
[error]   (x: Long)Double <and>
[error]   (x: Int)Double <and>
[error]   (x: Char)Double <and>
[error]   (x: Short)Double <and>
[error]   (x: Byte)Double
[error]  cannot be applied to (AnyVal)
[error]   val newnom = userRatings.leftOuterJoin(newUserAverages).map { case (u, (r, a)) => (u, r - a.getOrElse())}

代码：

val userRatings = train.map(x => (x._1, x._3))
  val userAverages = userRatings.groupBy(_._1).mapValues(_.map(_._2)).map{case (u, r) => (u, (r.sum/r.size).toDouble)}
  val newnom = userRatings.leftOuterJoin(userAverages).map { case (u, (r, a)) => (u, r - a.getOrElse())}

rdd元组在应用map之前是这样的（为什么我在.3元素上使用.getorelse）：

(451,(1.0,Some(2.7362637362637363)))
(451,(4.0,Some(2.7362637362637363)))
(451,(2.0,Some(2.7362637362637363)))
(451,(4.0,Some(2.7362637362637363)))
(451,(4.0,Some(2.7362637362637363)))

我基本上希望最后一个值从第二个值中减去，我希望从文本中可以清楚地看到。试图用多种方式转换数字，舍入，格式化等。。但还是会有同样的错误。