PIG：如何創建基於百分比（％）的表？

Question

我想創建一個表，將顯示百分比的出現次數。例如：我有一個表，命名爲例如包含數據爲：

class, value 
------ ------- 
1  , abc 
1  , abc 
1  , xyz 
1  , abc 
2  , xyz 
2  , abc 

這裏，對於類值1，「ABC」時發生3次和「XYZ」只發生一次出總髮生的的4倍。對於班級值2，「abc」和「xyz」發生一次（總共出現兩次）。

所以，輸出是：

class, %_of_abc, %_of_xyz 
------ -------- -------- 
1  , 75  , 25 
2  , 50  , 50 

任何想法如何做到這一點其中兩個列值發生改變？我正在考慮使用GROUP。但不知道我是否按照課程價值分組，如何幫助我。

Answer 1

有點複雜，但這裏的解決方案

grunt> Dump A; 
(1,abc) 
(1,abc) 
(1,xyz) 
(1,abc) 
(2,xyz) 
(2,abc) 
grunt> B = Group A by class; 
grunt> C = foreach B generate group as class:int, COUNT(A) as cnt; 
grunt> D = Group A by (class,value);   
grunt> E = foreach D generate FLATTEN(group), COUNT(A) as tot_cnt; 
grunt> F = foreach E generate $0 as class:int, $1 as value:chararray, tot_cnt; 
grunt> G = JOIN F BY class,C BY class; 
grunt> H = foreach G generate $0 as class,$1 as value,($2*100/$4) as perc; 
grunt> Dump H; 
(1,xyz,25) 
(1,abc,75) 
(2,xyz,50) 
(2,abc,50) 
I = grouy H by class; 
J = FOREACH I generate group as class, FLATTEN(BagToTuple(H.perc)); 
Dump J; 
(1,75,25) 
(2,50,50)