scala 获取数组列的大小/长度
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时间：2020-10-22 09:25:51 来源:igfitidea点击:
Get the size/length of an array column
提问by alukard990
I'm new in Scala programming and this is my question: How to count the number of string for each row? My Dataframe is composed of a single column of Array[String] type.
我是 Scala 编程的新手，这是我的问题：如何计算每行的字符串数？我的数据框由 Array[String] 类型的单列组成。
friendsDF: org.apache.spark.sql.DataFrame = [friends: array<string>]
回答by Psidom
You can use the sizefunction:
您可以使用该size功能：
val df = Seq((Array("a","b","c"), 2), (Array("a"), 4)).toDF("friends", "id")
// df: org.apache.spark.sql.DataFrame = [friends: array<string>, id: int]
df.select(size($"friends").as("no_of_friends")).show
+-------------+
|no_of_friends|
+-------------+
| 3|
| 1|
+-------------+
To add as a new column:
要添加为新列：
df.withColumn("no_of_friends", size($"friends")).show
+---------+---+-------------+
| friends| id|no_of_friends|
+---------+---+-------------+
|[a, b, c]| 2| 3|
| [a]| 4| 1|
+---------+---+-------------+
