豬羣中的簡單AVG？

Question

我有一個非常簡單的2列數據，一張雙人牀和一個chararray：

user1 234.43 
user1 432.23 
user2 4321.213 
etc. 

我想組用戶，然後計算他們的雙打的平均值。怎麼樣？我需要「GROUP * ALL」嗎？我試圖按照例2 http://wiki.apache.org/pig/PigOverview，但它不適合我。

selfReportsAndDiscrepancies = FOREACH discrepancies1 GENERATE discrepancy,selfReportedText; 
perDiscrepancy = GROUP selfReportsAndDiscrepancies BY selfReportedText; 

allDiscrep = group perDiscrepancy all; 

means = FOREACH allDiscrep GENERATE AVG(perDiscrepancy.discrepancy); 

DUMP means; 
DESCRIBE means; 

給我：

2013-04-02 17:54:06,611 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1128: Cannot find field discrepancy in group:chararray,selfReportsAndDiscrepancies:bag{:tuple(discrepancy:double,selfReportedText:chararray)} 

Answer 1

我希望我理解正確的，你想要的組平均數的平均值：

VISITS = LOAD 'data' USING PigStorage(' ') AS (user:chararray, number:double); 
USER_VISITS = GROUP VISITS BY user; 
USER_AVG = FOREACH USER_VISITS GENERATE group AS user, AVG(VISITS.number) AS average; 
ALL_AVG = GROUP USER_AVG ALL; 
OVERALL_AVG = FOREACH ALL_AVG GENERATE AVG(USER_AVG.average); 
DUMP OVERALL_AVG; 

結果：

(2327.2715)