PIG need to find max - apache-pig

Question

I am new to Pig and working on a problem where I need to find the the player in this dataset with the max weight. Here is a sample of the data:
id, weight,id,year, triples
(bayja01,210,bayja01,2005,6)
(crawfca02,225,crawfca02,2005,15)
(damonjo01,205,damonjo01,2005,6)
(dejesda01,190,dejesda01,2005,6)
(eckstda01,170,eckstda01,2005,7)
and here is my pig script:
batters = LOAD 'hdfs:/user/maria_dev/pigtest/Batting.csv' using PigStorage(',');
realbatters = FILTER batters BY $1==2005;
triphitters = FILTER realbatters BY $9>5;
tripids = FOREACH triphitters GENERATE $0 AS id,$1 AS YEAR, $9 AS Trips;
names = LOAD 'hdfs:/user/maria_dev/pigtest/Master.csv'
using PigStorage(',');
weights = FOREACH names GENERATE $0 AS id, $16 AS weight;
get_ids = JOIN weights BY (id), tripids BY(id);
wts = FOREACH get_ids GENERATE MAX(get_ids.weight)as wgt;
DUMP wts;
the second to last line did not work of course. It told me I had to use an explicit cast. I have the filtering etc figured out - jsut can't figure out how to get the final answer.

Answer 1

The MAX function in Pig expects a Bag of values and will return the highest value in the bag. In order to create a Bag, you must first GROUP your data:
get_ids = JOIN weights BY id, tripids BY id;
-- Drop columns we no longer need and rename for ease
just_ids_weights = FOREACH get_ids GENERATE
weights::id AS id,
weights:: weight AS weight;
-- Group the data by id value
gp_by_ids = GROUP just_ids_weights BY id;
-- Find maximum weight by id
wts = FOREACH gp_by_ids GENERATE
group AS id,
MAX(just_ids_weights.weight) AS wgt;
If you wanted the maximum weight in all of the data, you can put all of your data in a single bag using GROUP ALL:
gp_all = GROUP just_ids_weights ALL;
was = FOREACH gp_all GENERATE
MAX(just_ids_weights.weight) AS wgt;