假设我正在做这样的事情:
val df = sqlContext.load("com.databricks.spark.csv", Map("path" -> "cars.csv", "header" -> "true"))
df.printSchema()
root
|-- year: string (nullable = true)
|-- make: string (nullable = true)
|-- model: string (nullable = true)
|-- comment: string (nullable = true)
|-- blank: string (nullable = true)
df.show()
year make model comment blank
2012 Tesla S No comment
1997 Ford E350 Go get one now th...
但是我真的希望 year
是一个 Int
(并且可能转换其他列)。
我能想到的最好方法是:
df.withColumn("year2", 'year.cast("Int")).select('year2 as 'year, 'make, 'model, 'comment, 'blank)
org.apache.spark.sql.DataFrame = [year: int, make: string, model: string, comment: string, blank: string]
这有些复杂。
我的背景是R语言,我习惯于能够编写例如:
df2 <- df %>%
mutate(year = year %>% as.integer,
make = make %>% toupper)
我可能漏掉了一些东西,因为在Spark/Scala中应该有更好的方法来实现这个...