PIG: sum and division, creating an object

Question

I am writing a pig program that loads a file that separates its entires with tabs

ex: name TAB year TAB count TAB...

file = LOAD 'file.csv' USING PigStorage('\t') as (type: chararray, year: chararray,
match_count: float, volume_count: float);

-- Group by type
grouped = GROUP file BY type;

-- Flatten
by_type = FOREACH grouped GENERATE FLATTEN(group) AS (type, year, match_count, volume_count);

group_operat = FOREACH by_type GENERATE  
        SUM(match_count) AS sum_m,
        SUM(volume_count) AS sum_v,
       (float)sum_m/sm_v;

DUMP group_operat;

The issue lies in the group operations object I am trying to create. I'm wanting to sum all the match counts, sum all the volume counts and divide the match counts by volume counts.

What am I doing wrong in my arithmetic operations/object creation? An error I receive is line 7, column 11> pig script failed to validate: org.apache.pig.impl.logicalLayer.FrontendException: ERROR 1031: Incompatable schema: left is "type:NULL,year:NULL,match_count:NULL,volume_count:NULL", right is "group:chararray"

Thank you.

Answer 1

Try like this, this will return type and sum.

UPDATED the working code

input.txt

A       2001     10      2
A       2002     20      3
B       2003     30      4
B       2004     40      1

PigScript:

file = LOAD 'input.txt' USING PigStorage() AS (type: chararray, year: chararray,
match_count: float, volume_count: float);
grouped = GROUP file BY type;
group_operat = FOREACH grouped {
                                 sum_m = SUM(file.match_count);
                                 sum_v = SUM(file.volume_count);
                                 GENERATE group,(float)(sum_m/sum_v) as sum_mv;
                                }
DUMP group_operat;

Output:

(A,6.0)
(B,14.0)

Answer 2

try this,

file = LOAD 'file.csv' USING PigStorage('\t') as (type: chararray, year: chararray,
match_count: float, volume_count: float);

grouped = GROUP file BY (type,year);

group_operat = FOREACH grouped GENERATE group,
        SUM(file.match_count) AS sum_m,
        SUM(file.volume_count) AS sum_v,
       (float)(SUM(file.match_count)/SUM(file.volume_count)) as sum_mv;

Above script give result group by type and year, if you want only group by type then remove from grouped

grouped = GROUP file BY type;

group_operat = FOREACH grouped GENERATE group,file.year,
        SUM(file.match_count) AS sum_m,
        SUM(file.volume_count) AS sum_v,
       (float)(SUM(file.match_count)/SUM(file.volume_count)) as sum_mv;