(문법) Pandas Grouper

Pandas Grouper

API

class Grouper:
    """
    A Grouper allows the user to specify a groupby instruction for an object.
    This specification will select a column via the key parameter, or if the
    level and/or axis parameters are given, a level of the index of the target
    object.
    If `axis` and/or `level` are passed as keywords to both `Grouper` and
    `groupby`, the values passed to `Grouper` take precedence.
    Parameters
    ----------
    key : str, defaults to None
        Groupby key, which selects the grouping column of the target.
    level : name/number, defaults to None
        The level for the target index.
    freq : str / frequency object, defaults to None
        This will groupby the specified frequency if the target selection
        (via key or level) is a datetime-like object. For full specification
        of available frequencies, please see `here
        <https://pandas.pydata.org/pandas-docs/stable/user_guide/timeseries.html#offset-aliases>`_.
    axis : str, int, defaults to 0
        Number/name of the axis.
    sort : bool, default to False
        Whether to sort the resulting labels.
    closed : {'left' or 'right'}
        Closed end of interval. Only when `freq` parameter is passed.
    label : {'left' or 'right'}
        Interval boundary to use for labeling.
        Only when `freq` parameter is passed.
    convention : {'start', 'end', 'e', 's'}
        If grouper is PeriodIndex and `freq` parameter is passed.
    base : int, default 0
        Only when `freq` parameter is passed.
        For frequencies that evenly subdivide 1 day, the "origin" of the
        aggregated intervals. For example, for '5min' frequency, base could
        range from 0 through 4. Defaults to 0.
        .. deprecated:: 1.1.0
            The new arguments that you should use are 'offset' or 'origin'.
    loffset : str, DateOffset, timedelta object
        Only when `freq` parameter is passed.
        .. deprecated:: 1.1.0
            loffset is only working for ``.resample(...)`` and not for
            Grouper (:issue:`28302`).
            However, loffset is also deprecated for ``.resample(...)``
            See: :class:`DataFrame.resample`
    origin : {'epoch', 'start', 'start_day'}, Timestamp or str, default 'start_day'
        The timestamp on which to adjust the grouping. The timezone of origin must
        match the timezone of the index.
        If a timestamp is not used, these values are also supported:
        - 'epoch': `origin` is 1970-01-01
        - 'start': `origin` is the first value of the timeseries
        - 'start_day': `origin` is the first day at midnight of the timeseries
        .. versionadded:: 1.1.0
    offset : Timedelta or str, default is None
        An offset timedelta added to the origin.
        .. versionadded:: 1.1.0
    dropna : bool, default True
        If True, and if group keys contain NA values, NA values together with
        row/column will be dropped. If False, NA values will also be treated as
        the key in groups.
        .. versionadded:: 1.2.0
    Returns
    -------
    A specification for a groupby instruction

 

Example

1. 특정 속성의 키값의 그룹별 계산

>>> df = pd.DataFrame(
...     {
...         "Animal": ["Falcon", "Parrot", "Falcon", "Falcon", "Parrot"],
...         "Speed": [100, 5, 200, 300, 15],
...     }
... )
>>> df
Animal  Speed
0  Falcon    100
1  Parrot      5
2  Falcon    200
3  Falcon    300
4  Parrot     15
>>> df.groupby(pd.Grouper(key="Animal")).mean()
Speed
Animal
Falcon    200
Parrot     10

2. 시간값을가지는 속성의 기간 그룹별 계산

>>> df = pd.DataFrame(
...    {
...        "Publish date": [
...             pd.Timestamp("2000-01-02"),
...             pd.Timestamp("2000-01-02"),
...             pd.Timestamp("2000-01-09"),
...             pd.Timestamp("2000-01-16")
...         ],
...         "ID": [0, 1, 2, 3],
...         "Price": [10, 20, 30, 40]
...     }
... )
>>> df
Publish date  ID  Price
0   2000-01-02   0     10
1   2000-01-02   1     20
2   2000-01-09   2     30
3   2000-01-16   3     40
>>> df.groupby(pd.Grouper(key="Publish date", freq="1W")).mean()
ID  Price
Publish date
2000-01-02    0.5   15.0
2000-01-09    2.0   30.0
2000-01-16    3.0   40.0

3. 시간속성을 가지는 속성의 기간 및 시작조건별 계산

>>> start, end = '2000-10-01 23:30:00', '2000-10-02 00:30:00'
>>> rng = pd.date_range(start, end, freq='7min')
>>> ts = pd.Series(np.arange(len(rng)) * 3, index=rng)
>>> ts
2000-10-01 23:30:00     0
2000-10-01 23:37:00     3
2000-10-01 23:44:00     6
2000-10-01 23:51:00     9
2000-10-01 23:58:00    12
2000-10-02 00:05:00    15
2000-10-02 00:12:00    18
2000-10-02 00:19:00    21
2000-10-02 00:26:00    24
Freq: 7T, dtype: int64
>>> ts.groupby(pd.Grouper(freq='17min')).sum()
2000-10-01 23:14:00     0
2000-10-01 23:31:00     9
2000-10-01 23:48:00    21
2000-10-02 00:05:00    54
2000-10-02 00:22:00    24
Freq: 17T, dtype: int64
>>> ts.groupby(pd.Grouper(freq='17min', origin='epoch')).sum()
2000-10-01 23:18:00     0
2000-10-01 23:35:00    18
2000-10-01 23:52:00    27
2000-10-02 00:09:00    39
2000-10-02 00:26:00    24
Freq: 17T, dtype: int64
>>> ts.groupby(pd.Grouper(freq='17min', origin='2000-01-01')).sum()
2000-10-01 23:24:00     3
2000-10-01 23:41:00    15
2000-10-01 23:58:00    45
2000-10-02 00:15:00    45
Freq: 17T, dtype: int64

>>> ts.groupby(pd.Grouper(freq='17min', origin='start')).sum()
2000-10-01 23:30:00     9
2000-10-01 23:47:00    21
2000-10-02 00:04:00    54
2000-10-02 00:21:00    24
Freq: 17T, dtype: int64
>>> ts.groupby(pd.Grouper(freq='17min', offset='23h30min')).sum()
2000-10-01 23:30:00     9
2000-10-01 23:47:00    21
2000-10-02 00:04:00    54
2000-10-02 00:21:00    24
Freq: 17T, dtype: int64

>>> ts.groupby(pd.Grouper(freq='17min', offset='2min')).sum()
2000-10-01 23:16:00     0
2000-10-01 23:33:00     9
2000-10-01 23:50:00    36
2000-10-02 00:07:00    39
2000-10-02 00:24:00    24
Freq: 17T, dtype: int64

참고자료

pandas.pydata.org/docs/reference/api/pandas.Grouper.html

pandas.Grouper — pandas 1.2.4 documentation

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