重新采样并附加到相同的数据帧

Posted 2023-02-18

【中文标题】重新采样并附加到相同的数据帧

【英文标题】：resampling and appending to same dataframe

【发布时间】：2021-11-07 05:59:00

【问题描述】：

我有一个数据框，我想对其重新采样并将结果作为新列附加到原始数据框，

我有什么：

index = pd.date_range('1/1/2000', periods=9, freq='T')
series = pd.Series(range(9), index=index)
series

time                 value      
2000-01-01 00:00:00    0
2000-01-01 00:01:00    1
2000-01-01 00:02:00    2
2000-01-01 00:03:00    3
2000-01-01 00:04:00    4
2000-01-01 00:05:00    5
2000-01-01 00:06:00    6
2000-01-01 00:07:00    7
2000-01-01 00:08:00    8

我想要什么：

time                 value   mean_resampled
2000-01-01 00:00:00    0.         2
2000-01-01 00:01:00    1.         NaN
2000-01-01 00:02:00    2.         NaN
2000-01-01 00:03:00    3.         NaN
2000-01-01 00:04:00    4.         NaN         
2000-01-01 00:05:00    5.         6.5
2000-01-01 00:06:00    6.         NaN
2000-01-01 00:07:00    7.         NaN
2000-01-01 00:08:00    8.         NaN

注意：重采样频率为'5T'

【问题讨论】：

重采样的频率是多少？

刚刚修改了问题:)

现在好多了 :) 现在答案就是你所期望的 :)

【参考方案1】：

使用resample 计算平均值，使用concat 将Series 与新值合并。

>>> pd.concat([series, series.resample('5T').mean()], axis=1) \
      .rename(columns=0: 'value', 1: 'mean_resampled')

                     value  mean_resampled
2000-01-01 00:00:00      0             2.0
2000-01-01 00:01:00      1             NaN
2000-01-01 00:02:00      2             NaN
2000-01-01 00:03:00      3             NaN
2000-01-01 00:04:00      4             NaN
2000-01-01 00:05:00      5             6.5
2000-01-01 00:06:00      6             NaN
2000-01-01 00:07:00      7             NaN
2000-01-01 00:08:00      8             NaN

如果您的实际情况是DataFrame 而不是Series，您只需添加一个新列：

>>> df['mean_resampled'] = df.resample('5T').mean()

【参考方案2】：

index = pd.date_range('1/1/2000', periods=9, freq='T')
series = pd.Series(range(9), index=index, name='values')

sample = series.resample('5T').mean() # create a sample at some frequency
df = series.to_frame() # convert series to frame
df.loc[sample.index.values, 'mean_resampled'] = sample # use loc to assign new values

                     values  mean_resampled
2000-01-01 00:00:00       0             2.0
2000-01-01 00:01:00       1             NaN
2000-01-01 00:02:00       2             NaN
2000-01-01 00:03:00       3             NaN
2000-01-01 00:04:00       4             NaN
2000-01-01 00:05:00       5             6.5
2000-01-01 00:06:00       6             NaN
2000-01-01 00:07:00       7             NaN
2000-01-01 00:08:00       8             NaN