使用PIG计算平均值

Question

我是PIG的新手,想要计算我的一列数据的平均值

0
10.1
20.1
30
40
50
60
70
80.1

我写了这个猪脚本

dividends = load 'myfile.txt' as (A);
dump dividends
grouped   = group dividends by A;
avg       = foreach grouped generate AVG(grouped.A);
dump avg

它将数据解析为

(0)
(10.1)
(20.1)
(30)
(40)
(50)
(60)
(70)
(80.1)

但是平均给出了这个错误

2013-03-04 15:10:58,289 [main] ERROR org.apache.pig.tools.grunt.Grunt - ERROR 1200: Pig script failed to parse: 
<file try.pig, line 4, column 41> Invalid scalar projection: grouped
Details at logfile: /Users/PreetiGupta/Documents/CMPS290S/project/pig_1362438645642.log

任何的想法

Answer 1

该AVG内置功能需要一个袋子作为输入.在您的group陈述中,您当前按值的值对元素进行分组A,但您真正想要做的是将所有元素分组到一个包中.

猪GROUP ALL是你想要使用的:

dividends = load 'myfile.txt' as (A);
dump dividends
grouped   = group dividends all;
avg       = foreach grouped generate AVG(dividends.A);
dump avg

Answer 2

以下将用于计算平均值：

dividends = load 'myfile.txt' as (A);
grouped   = GROUP dividends all;
avg       = foreach grouped generate AVG(dividends);
dump avg