每年获得Apache Pig的最大值

Question

我一直在尝试使用以下数据获取每年的最高温度。实际数据看起来像这样，但我只对第一列（即年份）和第四列（即温度）感兴趣。

2016-11-03 12:00:00.000 +0100,Mostly Cloudy,rain,10.594444444444443,10.594444444444443,0.73,13.2664,174.0,10.1913,0.0,1019.74,Partly cloudy throughout the day.
2016-11-03 13:00:00.000 +0100,Mostly Cloudy,rain,11.072222222222223,11.072222222222223,0.72,13.1698,176.0,12.4131,0.0,1019.45,Partly cloudy throughout the day.
2016-11-03 14:00:00.000 +0100,Mostly Cloudy,rain,11.172222222222222,11.172222222222222,0.71,12.654600000000002,175.0,10.835300000000002,0.0,1019.16,Partly cloudy throughout the day.
2016-11-03 15:00:00.000 +0100,Mostly Cloudy,rain,10.911111111111111,10.911111111111111,0.72,11.753,170.0,10.867500000000001,0.0,1018.94,Partly cloudy throughout the day.
2016-11-03 16:00:00.000 +0100,Mostly Cloudy,rain,10.350000000000001,10.350000000000001,0.72,10.6582,161.0,11.592,0.0,1018.81,Partly cloudy throughout the day.
DUMP B is like below
(2014,12.038889)
(2014,21.055555) 
(2016,29.905556)
(2016,30.605556)
(2016,29.95)
(2016,29.972221)
我编写的代码如下。但是，它使我在D处出错。我也使用了ToDate函数，但似乎也无法正常工作。
A = load 'file.csv' using PigStorage(',')......
B = foreach A GENERATE SUBSTRING(year,0,4) as year1, Atemp
C = group B by year1;  
D = foreach C GENERATE group,MAX(Atemp);  
我得到错误：
Invalid field projection. Projected field [year1] does not exist in schema: group:chararray,B:bag{:tuple(year1:chararray,Atemp:float)}.
            
我一直在尝试使用以下数据获取每年的最高温度。实际数据看起来像这样，但是我只对第一列（即年份）和第四列（即温度）感兴趣。... ... >>

我在stackoverflow上发布问题后弄清楚了自己：)我不知道为什么！代替D = foreach C生成组，MAX（Atemp）;我已经使用D = foreach C GENERATE组，将MAX（B.Atemp）设置为max；而且有效！

[如果有人要我删除帖子，我很乐意删除。请让我知道

Answer 1

我在stackoverflow上发布问题后弄清楚了自己：)我不知道为什么！代替D = foreach C生成组，MAX（Atemp）;我已经使用D = foreach C GENERATE组，将MAX（B.Atemp）设置为max；而且有效！