python - Pandas 重新采样引发由日期时间对象组成的索引的类型错误

Question

我正在尝试对一个非常简单的数据帧进行重新采样，但失败并出现以下异常:

TypeError: Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of 'Index'

我阅读了 pandas API 文档并查看了数十个示例，但我无法弄清楚我做错了什么。

# %%
import pandas as pd
print(f"pandas version: {pd.__version__}\n\n")

data = pd.DataFrame({"created": ['2019-03-07T11:01:07.361+0000',
                                 '2019-06-05T15:09:51.203+0100',
                                 '2019-06-05T15:09:51.203+0100'],
                     "value": [10, 20, 30]})

# %%
print(f"original type: {type(data.created[0])}\n")
data.info()

# %%
data.created = pd.to_datetime(data.created)

# %%
print(f"updated type: {type(data.created[0])}\n")
data.info()

# %%
data.set_index("created", inplace=True)
data.info()

# %%
data.resample("D").mean()

这是结果

Pandas 版本:0.24.2

original type: <class 'str'>

<class 'pandas.core.frame.DataFrame'>
RangeIndex: 3 entries, 0 to 2
Data columns (total 2 columns):
created    3 non-null object
value      3 non-null int64
dtypes: int64(1), object(1)
memory usage: 128.0+ bytes

updated type: <class 'datetime.datetime'>

<class 'pandas.core.frame.DataFrame'>
RangeIndex: 3 entries, 0 to 2
Data columns (total 2 columns):
created    3 non-null object
value      3 non-null int64
dtypes: int64(1), object(1)
memory usage: 128.0+ bytes

<class 'pandas.core.frame.DataFrame'>
Index: 3 entries, 2019-03-07 11:01:07.361000+00:00 to 2019-06-05 15:09:51.203000+01:00
Data columns (total 1 columns):
value    3 non-null int64
dtypes: int64(1)
memory usage: 48.0+ bytes

Traceback (most recent call last):
  File "c:/Users/me/dev/misc/index.py", line 32, in <module>
    data.resample("D").mean()
  File "C:\Users\me\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\generic.py", line 8155, in resample
    base=base, key=on, level=level)
  File "C:\Users\me\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\resample.py", line 1250, in resample
    return tg._get_resampler(obj, kind=kind)
  File "C:\Users\me\AppData\Local\Continuum\anaconda3\lib\site-packages\pandas\core\resample.py", line 1380, in _get_resampler
    "but got an instance of %r" % type(ax).__name__)
TypeError: Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of 'Index'Index, but got an instance of 'Index'

Answer 1

让我们从一些原则开始:

1. 要进行重新采样，源Series或DataFrame必须具有例如 DatetimeIndex(不是“普通”索引)。

2. 您可以为该列设置索引，但为此，所有日期时间 元素必须位于相同时区(您的数据不是)。

因此您可以按照以下步骤操作:

1. 将创建的列转换为日期时间(代码的一部分)时， 传递utc=True来“统一”时区:

   data.created = pd.to_datetime(data.created, utc=True)
   

2. 设置索引，然后您可以自由地重新采样:

   data.set_index('created').resample("D").mean()
   

另一个选项:您可以传递on参数，而不是set_index， 指定日期时间(类似)列:

data.resample("D", on='created').mean()

但此列仍然必须包含同一时区的所有条目。