I have the following table:
我有下表：
Date Country Class Value
6/1/2010 USA A 45
6/1/2010 Canada A 23
6/1/2010 Brazil B 65
9/1/2010 USA B 47
9/1/2010 Canada A 98
9/1/2010 Brazil B 25
12/1/2010 USA B 14
12/1/2010 Canada A 79
12/1/2010 Brazil A 23
3/1/2011 USA A 84
3/1/2011 Canada B 77
3/1/2011 Brazil A 43
6/1/2011 USA A 45
6/1/2011 Canada A 23
6/1/2011 Brazil B 65
9/1/2011 USA B 47
9/1/2011 Canada A 98
9/1/2011 Brazil B 25
12/1/2011 USA B 14
12/1/2011 Canada A 79
12/1/2011 Brazil A 23
3/1/2012 USA A 84
3/1/2012 Canada B 77
3/1/2012 Brazil A 43
Date 
