Python-在 panda 数据框之间添加行

Question

我有一个像这样的数据框:

index = [0,1,2,3,4,5]
s = pd.Series([1,1,1,2,2,2],index= index)
t = pd.Series([2007,2008,2011,2006,2007,2009],index= index)
f = pd.Series([2,4,6,8,10,12],index= index)
pp =pd.DataFrame(np.c_[s,t,f],columns = ["group","year","amount"])
pp

   group    year    amount
0   1       2007    2
1   1       2008    4
2   1       2011    6
3   2       2006    8
4   2       2007    10
5   2       2009    12

我想在每个组的缺失年份之间添加行。我想要的数据框是这样的:

   group    year    amount
0   1.0     2007    2.0
1   1.0     2008    4.0
2   1.0     2009    NaN
3   1.0     2010    NaN
4   1.0     2011    6
5   1.0     2006    8.0
6   2.0     2007    10.0
7   2.0     2008    NaN
8   2.0     2009    12.0

有什么办法可以处理大型数据框吗？

Answer 1

首先将年份更改为日期时间:

df.year = pd.to_datetime(df.year, format='%Y')

set_index 和 resample

df.set_index('year').groupby('group').amount.resample('Y').mean().reset_index()

   group       year  amount
0      1 2007-12-31     2.0
1      1 2008-12-31     4.0
2      1 2009-12-31     NaN
3      1 2010-12-31     NaN
4      1 2011-12-31     6.0
5      2 2006-12-31     8.0
6      2 2007-12-31    10.0
7      2 2008-12-31     NaN
8      2 2009-12-31    12.0