Is there a way to apply an aggregate function to all (or a list of) columns of a dataframe, when doing a groupBy
? In other words, is there a way to avoid doing this for every column:
df.groupBy("col1")
.agg(sum("col2").alias("col2"), sum("col3").alias("col3"), ...)
This question is related to
apache-spark
dataframe
apache-spark-sql
aggregate-functions
Current answers are perfectly correct on how to create the aggregations, but none actually address the column alias/renaming that is also requested in the question.
Typically, this is how I handle this case:
val dimensionFields = List("col1")
val metrics = List("col2", "col3", "col4")
val columnOfInterests = dimensions ++ metrics
val df = spark.read.table("some_table").
.select(columnOfInterests.map(c => col(c)):_*)
.groupBy(dimensions.map(d => col(d)): _*)
.agg(metrics.map( m => m -> "sum").toMap)
.toDF(columnOfInterests:_*) // that's the interesting part
The last line essentially renames every columns of the aggregated dataframe to the original fields, essentially changing sum(col2)
and sum(col3)
to simply col2
and col3
.
Another example of the same concept - but say - you have 2 different columns - and you want to apply different agg functions to each of them i.e
f.groupBy("col1").agg(sum("col2").alias("col2"), avg("col3").alias("col3"), ...)
Here is the way to achieve it - though I do not yet know how to add the alias in this case
See the example below - Using Maps
val Claim1 = StructType(Seq(StructField("pid", StringType, true),StructField("diag1", StringType, true),StructField("diag2", StringType, true), StructField("allowed", IntegerType, true), StructField("allowed1", IntegerType, true)))
val claimsData1 = Seq(("PID1", "diag1", "diag2", 100, 200), ("PID1", "diag2", "diag3", 300, 600), ("PID1", "diag1", "diag5", 340, 680), ("PID2", "diag3", "diag4", 245, 490), ("PID2", "diag2", "diag1", 124, 248))
val claimRDD1 = sc.parallelize(claimsData1)
val claimRDDRow1 = claimRDD1.map(p => Row(p._1, p._2, p._3, p._4, p._5))
val claimRDD2DF1 = sqlContext.createDataFrame(claimRDDRow1, Claim1)
val l = List("allowed", "allowed1")
val exprs = l.map((_ -> "sum")).toMap
claimRDD2DF1.groupBy("pid").agg(exprs) show false
val exprs = Map("allowed" -> "sum", "allowed1" -> "avg")
claimRDD2DF1.groupBy("pid").agg(exprs) show false
Source: Stackoverflow.com