Spark Scala对两个数据框中的列进行一些数学运算

Question

我们有两个数据框：

+----+--------+--------+
| id | height | weight |
+----+--------+--------+
|  1 |    12  |      5 |
|  2 |      8 |      7 |
+----+--------+--------+

和另一个 ：

+----+------+--------+
| id | Area | Area_2 |
+----+------+--------+
|  1 |      |        |
|  2 |      |        |
+----+------+--------+

我需要通过id将两个数据帧连接起来，并导致第二个df必须是这样的：

+----+---------+--------+
| id |  Area   | Area_2 |
+----+---------+--------+
|  1 | (12*5)  | (12+5) |
|  2 | (8*7)   | (8+7)  |
+----+---------+--------+

（其中Area和Area_2需要具有来自另一个DF的高度和重量之间的运算结果，并由id连接）

Answer 1

试试下面的代码

  val df1 = Seq((1, 12, 5), (2,8,7)).toDF("id", "height", "weight")
  val df2 = Seq((1),(2)).toDF("id") // drop area and area2 columns from this df
  val df3 = df1.withColumn("area", col("height")* col("weight")).withColumn("area2", col("height") + col("weight"))
  val finaldf = df2.join(df3, Seq("id"))

  scala> finaldf.show
  +---+------+------+----+-----+
  | id|height|weight|area|area2|
  +---+------+------+----+-----+
  |  1|    12|     5|  60|   17|
  |  2|     8|     7|  56|   15|
  +---+------+------+----+-----+