Count the grouped records in pig query - apache-pig

Question

Below is my test data.
John,q1,Correct
Jack,q1,wrong
John,q2,Correct
Jack,q2,wrong
John,q3,wrong
Jack,q3,Correct
John,q4,wrong
Jack,q4,wrong
John,q5,wrong
Jack,q5,wrong
I want to find something like below:
John wrong 4
John correct 1
Jack wrong 3
Jack correct 2
My Code:
data = LOAD '/stackoverflowq4.txt' USING PigStorage(',') AS (
name:chararray,
number:chararray,
result:chararray);
B = GROUP data by (name,result);
Now the out put looks like below:
((John,wrong),{(John,q5,wrong),(John,q4,wrong),(John,q2,wrong),(John,q1,wrong)})
((John,Correct),{(John,q3,Correct)})
((Jack,wrong),{(Jack,q5,wrong),(Jack,q4,wrong),(Jack,q3,wrong)})
((Jack,Correct),{(Jack,q2,Correct),(Jack,q1,Correct)})
How should I calculate count the grouped records.

Answer 1

The COUNT function will give you the number of elements in a bag, which is exactly what you want. After grouping by user and result, you end up with a bag with the number of times each combination appeared.
Therefore, you only have to add one line:
data = LOAD '/stackoverflowq4.txt' USING PigStorage(',') AS (
name:chararray,
number:chararray,
result:chararray);
B = GROUP data by (name,result);
C = foreach B generate FLATTEN(group) as (name,result), COUNT(data) as count;
dump D;
(Jack,wrong,4)
(Jack,Correct,1)
(John,wrong,3)
(John,Correct,2)
The FLATTEN(group) is because after grouping, a tuple containing the elements you grouped by is generated, and by the looks of what you want as output you don't want it inside a tuple, as the output would be like ((Jack,wrong),4).