pig tutorial - apache pig tutorial - Calculate Average using PIG ? - pig latin - apache pig - pig hadoop
What is Avg()
- The Pig-Latin AVG() function is used to compute the average of the numerical values within a bag. While calculating the average value, the AVG() function ignores the NULL values.
- To get the global average value, we need to perform a Group All operation, and calculate the average value using the AVG() function.
- To get the average value of a group, we need to group it using the Group By operator and proceed with the average function.
Syntax
- Here is the syntax of the AVG() function.
grunt> AVG(expression)
Example
- Assume that we have a file named employees_details.txt in the HDFS directory /pig_data/ as shown below.
employees_details.txt
001,Rajiv,Reddy,21,9848022337,Hyderabad,89
002,siddarth,Battacharya,22,9848022338,Kolkata,78
003,Rajesh,Khanna,22,9848022339,Delhi,90
004,Preethi,Agarwal,21,9848022330,Pune,93
005,Trupthi,Mohanthy,23,9848022336,Bhuwaneshwar,75
006,Archana,Mishra,23,9848022335,Chennai,87
- We have loaded this file into Pig with the relation name employees_details as shown below.
grunt> student_details = LOAD 'hdfs://localhost:9000/pig_data/student_details.txt' USING PigStorage(',')
as (id:int, firstname:chararray, lastname:chararray, age:int, phone:chararray, city:chararray, gpa:int);
Calculating the Average GPA
- The built-in function AVG() (case-sensitive) is helps to calculate the average of a set of numerical values. Let’s group the relation employee_details using the Group All operator, and store the result in the relation named employee_group_all as shown below.
grunt> student_group_all = Group student_details All;
- This gives the relationship as below.
grunt> Dump student_group_all;
(all,{(8,Bharathi,Nambiayar,24,9848022333,Chennai,72),
(7,Komal,Nayak,24,9848022 334,trivendram,83),
(6,Archana,Mishra,23,9848022335,Chennai,87),
(5,Trupthi,Mohan thy,23,9848022336,Bhuwaneshwar,75),
(4,Preethi,Agarwal,21,9848022330,Pune,93),
(3 ,Rajesh,Khanna,22,9848022339,Delhi,90),
(2,siddarth,Battacharya,22,9848022338,Ko lkata,78),
(1,Rajiv,Reddy,21,9848022337,Hyderabad,89)})