Unable to recognise windowing function in intellij

Question : Unable to recognize avg and over function in IntelliJ. It is saying cannot resolve symbol avg and over. Can someone please say which library to import.

import org.apache.spark.sql.functions._

is something you are missing.. for function avg

import org.apache.spark.sql.expressions.Window 

is import for Window.

see this complete example which is working...

  package com.examples

import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.expressions.Window

object DomainSpecificLanguage {
  def main(args: Array[String]): Unit = {
    System.setProperty("hadoop.home.dir", "C:/winutils")
    val spark = SparkSession.builder().appName("DomainSpecificLanguage").config("spark.master", "local").getOrCreate()
    spark.sparkContext.setLogLevel("ERROR")
    import spark.implicits._
    val empSalary = Seq(
      Salary("sales", 1, 5000),
      Salary("personnel", 2, 3900),
      Salary("sales", 3, 4800),
      Salary("sales", 4, 4800),
      Salary("personnel", 5, 3500),
      Salary("develop", 7, 4200),
      Salary("develop", 8, 6000),
      Salary("develop", 9, 4500),
      Salary("develop", 10, 5200),
      Salary("develop", 11, 5200)).toDS()
    val byDepName = Window.partitionBy('depName)
    import org.apache.spark.sql.functions._
    empSalary.withColumn("avg", avg('salary) over byDepName).show
  }

}

case class Salary(depName: String, deptnumber: Int, salary: Int)

Result :

+---------+----------+------+-----------------+
|  depName|deptnumber|salary|              avg|
+---------+----------+------+-----------------+
|  develop|         7|  4200|           5020.0|
|  develop|         8|  6000|           5020.0|
|  develop|         9|  4500|           5020.0|
|  develop|        10|  5200|           5020.0|
|  develop|        11|  5200|           5020.0|
|    sales|         1|  5000|4866.666666666667|
|    sales|         3|  4800|4866.666666666667|
|    sales|         4|  4800|4866.666666666667|
|personnel|         2|  3900|           3700.0|
|personnel|         5|  3500|           3700.0|
+---------+----------+------+-----------------+

From following the instructions on this website: https://jaceklaskowski.gitbooks.io/mastering-spark-sql/spark-sql-functions-windows.html

import org.apache.spark.sql.expressions.Window

There will be a lot of other useful guidance on Window functions at the above URL.