我有这个数据框,我想要一个新的,对于每个国家,我都有年数集的‘计数’平均值
country Alpha-3 code Year Count
0 Australia AUS 2005 2.000000
1 Austria AUT 2005 1.000000
2 Belgium BEL 2005 0.000000
3 Canada CAN 2005 4.000000
4 China CHN 2005 0.000000
5 Australia AUS 2006 4.000000
6 Austria AUT 2006 1.000000
7 Belgium BEL 2006 1.000000
8 Canada CAN 2006 6.000000
9 China CHN 2006 2.000000
10 Australia AUS 2007 5.000000
11 Austria AUT 2007 0.000000
12 Belgium BEL 2007 2.000000
13 Canada CAN 2007 5.000000
14 China CHN 2007 3.000000
15 Australia AUS 2008 7.000000
16 Austria AUT 2008 0.000000
17 Belgium BEL 2008 1.000000
18 Canada CAN 2008 5.000000
19 China CHN 2008 3.000000
我想要一个这样的东西:
country Count
Australia 4.5
Austria 0.5
ecc.
提前谢谢你