I'd like to append (add) a new column to an existing dataframe with multiple columns.
val a = Seq(
("10", "MILLER", "1300", "2017-11-03"),
("30", "Martin", "1250", "2017-11-21")).toDF("dept_no","emp_name","sal","date")
scala> a.show
+-------+--------+----+----------+
|dept_no|emp_name| sal| date|
+-------+--------+----+----------+
| 10| MILLER|1300|2017-11-03|
| 30| Martin|1250|2017-11-21|
+-------+--------+----+----------+
With the above dataframe I'd like to add every element of a collection (be it a regular Scala collection or another single-column DataFrame), e.g.
val lst = List("10", "Susan")
How to add the elements of lst above to the rows of a dataframe (one element per row)?
Let's convert lst to a DataFrame:
val lst = List("10", "Susan").toDF
You can use zip method of RDD:
import org.apache.spark.sql.Row
val data = a.rdd.zip(lst.rdd).map { case (l, r) => Row.fromSeq(l.toSeq ++ r.toSeq) }
import org.apache.spark.sql.types.StructType
val schema = StructType(a.schema.fields ++ lst.schema.fields)
val solution = spark.createDataFrame(data, schema)
scala> solution.show
+-------+--------+----+----------+-----+
|dept_no|emp_name| sal| date|value|
+-------+--------+----+----------+-----+
| 10| MILLER|1300|2017-11-03| 10|
| 30| Martin|1250|2017-11-21|Susan|
+-------+--------+----+----------+-----+
I have a Spark DataFrame where I have a column with Vector values. The vector values are all n-dimensional, aka with the same length. I also have a list of column names Array("f1", "f2", "f3", ..., "fn"), each corresponds to one element in the vector.
some_columns... | Features
... | [0,1,0,..., 0]
to
some_columns... | f1 | f2 | f3 | ... | fn
... | 0 | 1 | 0 | ... | 0
What is the best way to achieve this? I thought of one way which is to create a new DataFrame with createDataFrame(Row(Features), featureNameList) and then join with the old one, but it requires spark context to use createDataFrame. I only want to transform the existing data frame. I also know .withColumn("fi", value) but what do I do if n is large?
I'm new to Scala and Spark and couldn't find any good examples for this. I think this can be a common task. My particular case is that I used the CountVectorizer and wanted to recover each column individually for better readability instead of only having the vector result.
One way could be to convert the vector column to an array<double> and then using getItem to extract individual elements.
import org.apache.spark.sql.functions._
import org.apache.spark.ml._
val df = Seq( (1 , linalg.Vectors.dense(1,0,1,1,0) ) ).toDF("id", "features")
//df: org.apache.spark.sql.DataFrame = [id: int, features: vector]
df.show
//+---+---------------------+
//|id |features |
//+---+---------------------+
//|1 |[1.0,0.0,1.0,1.0,0.0]|
//+---+---------------------+
// A UDF to convert VectorUDT to ArrayType
val vecToArray = udf( (xs: linalg.Vector) => xs.toArray )
// Add a ArrayType Column
val dfArr = df.withColumn("featuresArr" , vecToArray($"features") )
// Array of element names that need to be fetched
// ArrayIndexOutOfBounds is not checked.
// sizeof `elements` should be equal to the number of entries in column `features`
val elements = Array("f1", "f2", "f3", "f4", "f5")
// Create a SQL-like expression using the array
val sqlExpr = elements.zipWithIndex.map{ case (alias, idx) => col("featuresArr").getItem(idx).as(alias) }
// Extract Elements from dfArr
dfArr.select(sqlExpr : _*).show
//+---+---+---+---+---+
//| f1| f2| f3| f4| f5|
//+---+---+---+---+---+
//|1.0|0.0|1.0|1.0|0.0|
//+---+---+---+---+---+
I have a dataframe of format given below.
movieId1 | genreList1 | genreList2
--------------------------------------------------
1 |[Adventure,Comedy] |[Adventure]
2 |[Animation,Drama,War] |[War,Drama]
3 |[Adventure,Drama] |[Drama,War]
and trying to create another flag column which shows whether genreList2 is a subset of genreList1.
movieId1 | genreList1 | genreList2 | Flag
---------------------------------------------------------------
1 |[Adventure,Comedy] | [Adventure] |1
2 |[Animation,Drama,War] | [War,Drama] |1
3 |[Adventure,Drama] | [Drama,War] |0
I have tried this:
def intersect_check(a: Array[String], b: Array[String]): Int = {
if (b.sameElements(a.intersect(b))) { return 1 }
else { return 2 }
}
def intersect_check_udf =
udf((colvalue1: Array[String], colvalue2: Array[String]) => intersect_check(colvalue1, colvalue2))
data = data.withColumn("Flag", intersect_check_udf(col("genreList1"), col("genreList2")))
But this throws error
org.apache.spark.SparkException: Failed to execute user defined function.
P.S.: The above function (intersect_check) works for Arrays.
We can define an udf that calculates the length of the intersection between the two Array columns and checks whether it is equal to the length of the second column. If so, the second array is a subset of the first one.
Also, the inputs of your udf need to be class WrappedArray[String], not Array[String] :
import scala.collection.mutable.WrappedArray
import org.apache.spark.sql.functions.col
val same_elements = udf { (a: WrappedArray[String],
b: WrappedArray[String]) =>
if (a.intersect(b).length == b.length){ 1 }else{ 0 }
}
df.withColumn("test",same_elements(col("genreList1"),col("genreList2")))
.show(truncate = false)
+--------+-----------------------+------------+----+
|movieId1|genreList1 |genreList2 |test|
+--------+-----------------------+------------+----+
|1 |[Adventure, Comedy] |[Adventure] |1 |
|2 |[Animation, Drama, War]|[War, Drama]|1 |
|3 |[Adventure, Drama] |[Drama, War]|0 |
+--------+-----------------------+------------+----+
Data
val df = List((1,Array("Adventure","Comedy"), Array("Adventure")),
(2,Array("Animation","Drama","War"), Array("War","Drama")),
(3,Array("Adventure","Drama"),Array("Drama","War"))).toDF("movieId1","genreList1","genreList2")
Here is the solution converting using subsetOf
val spark =
SparkSession.builder().master("local").appName("test").getOrCreate()
import spark.implicits._
val data = spark.sparkContext.parallelize(
Seq(
(1,Array("Adventure","Comedy"),Array("Adventure")),
(2,Array("Animation","Drama","War"),Array("War","Drama")),
(3,Array("Adventure","Drama"),Array("Drama","War"))
)).toDF("movieId1", "genreList1", "genreList2")
val subsetOf = udf((col1: Seq[String], col2: Seq[String]) => {
if (col2.toSet.subsetOf(col1.toSet)) 1 else 0
})
data.withColumn("flag", subsetOf(data("genreList1"), data("genreList2"))).show()
Hope this helps!
One solution may be to exploit spark array builtin functions: genreList2 is subset of genreList1 if the intersection between the two is equal to genreList2. In the code below a sort_array operation has been added to avoid a mismatch between two arrays with different ordering but same elements.
val spark = {
SparkSession
.builder()
.master("local")
.appName("test")
.getOrCreate()
}
import spark.implicits._
import org.apache.spark.sql._
import org.apache.spark.sql.functions._
val df = Seq(
(1, Array("Adventure","Comedy"), Array("Adventure")),
(2, Array("Animation","Drama","War"), Array("War","Drama")),
(3, Array("Adventure","Drama"), Array("Drama","War"))
).toDF("movieId1", "genreList1", "genreList2")
df
.withColumn("flag",
sort_array(array_intersect($"genreList1",$"genreList2"))
.equalTo(
sort_array($"genreList2")
)
.cast("integer")
)
.show()
The output is
+--------+--------------------+------------+----+
|movieId1| genreList1| genreList2|flag|
+--------+--------------------+------------+----+
| 1| [Adventure, Comedy]| [Adventure]| 1|
| 2|[Animation, Drama...|[War, Drama]| 1|
| 3| [Adventure, Drama]|[Drama, War]| 0|
+--------+--------------------+------------+----+
This can also work here and it does not use udf
import spark.implicits._
val data = Seq(
(1,Array("Adventure","Comedy"),Array("Adventure")),
(2,Array("Animation","Drama","War"),Array("War","Drama")),
(3,Array("Adventure","Drama"),Array("Drama","War"))
).toDF("movieId1", "genreList1", "genreList2")
data
.withColumn("size",size(array_except($"genreList2",$"genreList1")))
.withColumn("flag",when($"size" === lit(0), 1) otherwise(0))
.show(false)
Spark 3.0+ (forall)
forall($"genreList2", x => array_contains($"genreList1", x)).cast("int")
Full example:
val df = Seq(
(1, Seq("Adventure", "Comedy"), Seq("Adventure")),
(2, Seq("Animation", "Drama","War"), Seq("War", "Drama")),
(3, Seq("Adventure", "Drama"), Seq("Drama", "War"))
).toDF("movieId1", "genreList1", "genreList2")
val df2 = df.withColumn("Flag", forall($"genreList2", x => array_contains($"genreList1", x)).cast("int"))
df2.show()
// +--------+--------------------+------------+----+
// |movieId1| genreList1| genreList2|Flag|
// +--------+--------------------+------------+----+
// | 1| [Adventure, Comedy]| [Adventure]| 1|
// | 2|[Animation, Drama...|[War, Drama]| 1|
// | 3| [Adventure, Drama]|[Drama, War]| 0|
// +--------+--------------------+------------+----+
I need to write one scenario in Spark using Scala API.
I am passing a user defined function to a Dataframe which processes each row of data frame one by one and returns tuple(Row, Row). How can i change RDD ( Row, Row) to Dataframe (Row)? See below code sample -
**Calling map function-**
val df_temp = df_outPut.map { x => AddUDF.add(x,date1,date2)}
**UDF definition.**
def add(x: Row,dates: String*): (Row,Row) = {
......................
........................
var result1,result2:Row = Row()
..........
return (result1,result2)
Now df_temp is a RDD(Row1, Row2). my requirement is to make it one RDD or Dataframe by breaking tuple elements to 1 record of RDD or Dataframe
RDD(Row). Appreciate your help.
You can use flatMap to flatten your Row tuples, say if we start from this example rdd:
rddExample.collect()
// res37: Array[(org.apache.spark.sql.Row, org.apache.spark.sql.Row)] = Array(([1,2],[3,4]), ([2,1],[4,2]))
val flatRdd = rddExample.flatMap{ case (x, y) => List(x, y) }
// flatRdd: org.apache.spark.rdd.RDD[org.apache.spark.sql.Row] = MapPartitionsRDD[45] at flatMap at <console>:35
To convert it to data frame.
import org.apache.spark.sql.types.{StructType, StructField, IntegerType}
val schema = StructType(StructField("x", IntegerType, true)::
StructField("y", IntegerType, true)::Nil)
val df = sqlContext.createDataFrame(flatRdd, schema)
df.show
+---+---+
| x| y|
+---+---+
| 1| 2|
| 3| 4|
| 2| 1|
| 4| 2|
+---+---+
I am using a vector assembler to transform a dataframe.
var stringAssembler = new VectorAssembler().setInputCols(encodedstringColumns).setOutputCol("stringFeatures")
df = stringAssembler.transform(df)
**var stringVectorSize = df.select("stringFeatures").head.size**
var stringPca = new PCA().setInputCol("stringFeatures").setOutputCol("pcaStringFeatures").setK(stringVectorSize).fit(output)
Now stringVectorSize will tell PCA how many columns to keep while performing pca.
I am trying to get the size of the output sparse vector from the vector assembler but my code gives size = 1 which is wrong. What is the right code to get the size of a sparse vector which is the part of a dataframe column.
To put it plainly
+-------------+------------+-------------+------------+---+-----------+---------------+-----------------+--------------------+
|PetalLengthCm|PetalWidthCm|SepalLengthCm|SepalWidthCm| Id| Species|Species_Encoded| Id_Encoded| stringFeatures|
+-------------+------------+-------------+------------+---+-----------+---------------+-----------------+--------------------+
| 1.4| 0.2| 5.1| 3.5| 1|Iris-setosa| (2,[0],[1.0])| (149,[91],[1.0])|(151,[91,149],[1....|
| 1.4| 0.2| 4.9| 3.0| 2|Iris-setosa| (2,[0],[1.0])|(149,[119],[1.0])|(151,[119,149],[1...|
| 1.3| 0.2| 4.7| 3.2| 3|Iris-setosa| (2,[0],[1.0])|(149,[140],[1.0])|(151,[140,149],[1...|
For the above dataframe . I want to extract the size of stringFeatures sparse vector ( which is 151)
If you read DataFrame's documentation you will notice that the head method returns a Row. Therefore, rather than obtaining your SparseVector's size, you are obtaining Row's size. Thus, to solve this you have to extract the element stored in the Row.
val row = df.select("stringFeatures").head
val vector = vector(0).asInstanceOf[SparseVector]
val size = vector.size
For instance:
import sqlContext.implicits._
import org.apache.spark.mllib.linalg.SparseVector
val df = sc.parallelize(Array(10,2,3,4)).toDF("n")
val pepe = udf((i: Int) => new SparseVector(i, Array(i-1), Array(i)))
val x = df.select(pepe(df("n")).as("n"))
x.show()
+---------------+
| n|
+---------------+
|(10,[9],[10.0])|
| (2,[1],[2.0])|
| (3,[2],[3.0])|
| (4,[3],[4.0])|
+---------------+
val y = x.select("n").head
y(0).asInstanceOf[SparseVector].size
res12: Int = 10