Spark，在Scala中添加具有相同值的新列[重复]

Question

Spark-Scala环境中的WithColumn函数有一些问题。我想在我的DataFrame中添加一个新列，如下所示：

+---+----+---+
|  A|   B|  C|
+---+----+---+
|  4|blah|  2|
|  2|    |  3|
| 56| foo|  3|
|100|null|  5|
+---+----+---+

变成：

+---+----+---+-----+
|  A|   B|  C|  D  |
+---+----+---+-----+
|  4|blah|  2|  750|
|  2|    |  3|  750|
| 56| foo|  3|  750|
|100|null|  5|  750|
+---+----+---+-----+

var totVehicles : Double = df_totVehicles(0).getDouble(0); //return 750

var df_nVehicles =
df_carPark.filter(
      substring($"id_time",1,4) < 2013
    ).groupBy(
      $"id_zipcode"
    ).agg(
      sum($"n_vehicles") as 'n_vehicles
    ).select(
      $"id_zipcode" as 'id_zipcode,
      'n_vehicles
    ).orderBy(
      'id_zipcode,
      'n_vehicles
    );

var df_nVehicles2 = df_nVehicles.withColumn(totVehicles, df_nVehicles("n_vehicles") + df_nVehicles("id_zipcode"))

但是Spark返回给我这个错误：

 error: value withColumn is not a member of Unit
         var df_nVehicles2 = df_nVehicles.withColumn(totVehicles, df_nVehicles("n_vehicles") + df_nVehicles("id_zipcode"))

你能帮我吗？非常感谢！

Answer 1

lit函数用于将文字值添加为列

import org.apache.spark.sql.functions._
df.withColumn("D", lit(750))