如何用python计算月平均值？

Question

我有一个数据帧，每个用户的天数和下载量：

dates           downloadsperuser
2004-01-02  12.51118760757315
2004-01-03  6.990049751243781
2004-01-04  6.8099547511312215
2004-01-05  22.513349514563107
2004-01-06  22.348538011695908
2004-01-07  23.895180722891567
2004-01-08  21.765680473372782
2004-01-09  20.34256926952141
2004-01-10  9.455938697318008
...
2004-02-01  9.196078431372548
2004-02-02  21.558398220244715
2004-02-03  22.293007769145394
2004-02-04  22.324115044247787
2004-02-05  21.88482834994463
2004-02-06  20.236781609195404
2004-02-07  10.708823529411765
2004-02-08  10.835329341317365
2004-02-09  24.87350054525627
2004-02-10  24.167035398230087
2004-02-11  22.676117775354417
2004-02-12  23.384444444444444
2004-02-13  20.674285714285713
2004-02-14  10.74914089347079
2004-02-15  11.64873417721519
...
2004-03-01  23.36965811965812
2004-03-02  23.127545551982852
2004-03-03  23.60235798499464
2004-03-04  23.634015069967706
2004-03-05  20.468996617812852
2004-03-06  6.608208955223881
2004-03-07  5.570446735395189
2004-03-08  23.48093220338983
2004-03-09  25.734190782422292
2004-03-10  24.919652551574377
...

我要计算平均值。到目前为止，我试过：

^{pr2}$

成为一个月的日子。但我不知道如何才能将每月downloadsperuser列中的所有值相加。。在

Answer 1

你可以试试：

df.date = pd.to_datetime(df.date)

df_2 = df.groupby(df.date.dt.strftime('%Y-%m')).downloadsperuser.agg(['mean'])

Answer 2

首先计算月份和年份，然后按groupby计算平均值：

df['month'] = pd.to_datetime(df['date']).dt.month
df['year'] = pd.to_datetime(df['date']).dt.year
df.groupby(['year','month'],as_index=False).mean()