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603 lines
17 KiB
Python
603 lines
17 KiB
Python
from __future__ import annotations
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from typing import TYPE_CHECKING
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import numpy as np
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from pandas._libs import lib
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from pandas._libs.algos import unique_deltas
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from pandas._libs.tslibs import (
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Timestamp,
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get_unit_from_dtype,
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periods_per_day,
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tz_convert_from_utc,
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)
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from pandas._libs.tslibs.ccalendar import (
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DAYS,
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MONTH_ALIASES,
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MONTH_NUMBERS,
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MONTHS,
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int_to_weekday,
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)
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from pandas._libs.tslibs.dtypes import (
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OFFSET_TO_PERIOD_FREQSTR,
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freq_to_period_freqstr,
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)
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from pandas._libs.tslibs.fields import (
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build_field_sarray,
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month_position_check,
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)
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from pandas._libs.tslibs.offsets import (
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DateOffset,
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Day,
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to_offset,
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)
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from pandas._libs.tslibs.parsing import get_rule_month
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from pandas.util._decorators import cache_readonly
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from pandas.core.dtypes.common import is_numeric_dtype
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from pandas.core.dtypes.dtypes import (
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DatetimeTZDtype,
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PeriodDtype,
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)
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from pandas.core.dtypes.generic import (
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ABCIndex,
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ABCSeries,
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)
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from pandas.core.algorithms import unique
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if TYPE_CHECKING:
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from pandas._typing import npt
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from pandas import (
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DatetimeIndex,
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Series,
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TimedeltaIndex,
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)
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from pandas.core.arrays.datetimelike import DatetimeLikeArrayMixin
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# --------------------------------------------------------------------
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# Offset related functions
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_need_suffix = ["QS", "BQE", "BQS", "YS", "BYE", "BYS"]
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for _prefix in _need_suffix:
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for _m in MONTHS:
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key = f"{_prefix}-{_m}"
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OFFSET_TO_PERIOD_FREQSTR[key] = OFFSET_TO_PERIOD_FREQSTR[_prefix]
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for _prefix in ["Y", "Q"]:
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for _m in MONTHS:
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_alias = f"{_prefix}-{_m}"
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OFFSET_TO_PERIOD_FREQSTR[_alias] = _alias
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for _d in DAYS:
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OFFSET_TO_PERIOD_FREQSTR[f"W-{_d}"] = f"W-{_d}"
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def get_period_alias(offset_str: str) -> str | None:
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"""
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Alias to closest period strings BQ->Q etc.
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"""
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return OFFSET_TO_PERIOD_FREQSTR.get(offset_str, None)
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# ---------------------------------------------------------------------
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# Period codes
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def infer_freq(
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index: DatetimeIndex | TimedeltaIndex | Series | DatetimeLikeArrayMixin,
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) -> str | None:
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"""
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Infer the most likely frequency given the input index.
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Parameters
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----------
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index : DatetimeIndex, TimedeltaIndex, Series or array-like
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If passed a Series will use the values of the series (NOT THE INDEX).
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Returns
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-------
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str or None
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None if no discernible frequency.
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Raises
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------
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TypeError
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If the index is not datetime-like.
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ValueError
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If there are fewer than three values.
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Examples
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--------
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>>> idx = pd.date_range(start='2020/12/01', end='2020/12/30', periods=30)
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>>> pd.infer_freq(idx)
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'D'
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"""
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from pandas.core.api import DatetimeIndex
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if isinstance(index, ABCSeries):
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values = index._values
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if not (
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lib.is_np_dtype(values.dtype, "mM")
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or isinstance(values.dtype, DatetimeTZDtype)
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or values.dtype == object
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):
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raise TypeError(
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"cannot infer freq from a non-convertible dtype "
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f"on a Series of {index.dtype}"
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)
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index = values
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inferer: _FrequencyInferer
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if not hasattr(index, "dtype"):
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pass
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elif isinstance(index.dtype, PeriodDtype):
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raise TypeError(
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"PeriodIndex given. Check the `freq` attribute "
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"instead of using infer_freq."
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)
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elif lib.is_np_dtype(index.dtype, "m"):
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# Allow TimedeltaIndex and TimedeltaArray
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inferer = _TimedeltaFrequencyInferer(index)
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return inferer.get_freq()
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elif is_numeric_dtype(index.dtype):
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raise TypeError(
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f"cannot infer freq from a non-convertible index of dtype {index.dtype}"
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)
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if not isinstance(index, DatetimeIndex):
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index = DatetimeIndex(index)
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inferer = _FrequencyInferer(index)
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return inferer.get_freq()
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class _FrequencyInferer:
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"""
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Not sure if I can avoid the state machine here
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"""
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def __init__(self, index) -> None:
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self.index = index
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self.i8values = index.asi8
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# For get_unit_from_dtype we need the dtype to the underlying ndarray,
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# which for tz-aware is not the same as index.dtype
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if isinstance(index, ABCIndex):
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# error: Item "ndarray[Any, Any]" of "Union[ExtensionArray,
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# ndarray[Any, Any]]" has no attribute "_ndarray"
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self._creso = get_unit_from_dtype(
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index._data._ndarray.dtype # type: ignore[union-attr]
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)
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else:
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# otherwise we have DTA/TDA
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self._creso = get_unit_from_dtype(index._ndarray.dtype)
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# This moves the values, which are implicitly in UTC, to the
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# the timezone so they are in local time
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if hasattr(index, "tz"):
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if index.tz is not None:
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self.i8values = tz_convert_from_utc(
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self.i8values, index.tz, reso=self._creso
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)
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if len(index) < 3:
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raise ValueError("Need at least 3 dates to infer frequency")
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self.is_monotonic = (
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self.index._is_monotonic_increasing or self.index._is_monotonic_decreasing
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)
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@cache_readonly
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def deltas(self) -> npt.NDArray[np.int64]:
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return unique_deltas(self.i8values)
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@cache_readonly
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def deltas_asi8(self) -> npt.NDArray[np.int64]:
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# NB: we cannot use self.i8values here because we may have converted
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# the tz in __init__
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return unique_deltas(self.index.asi8)
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@cache_readonly
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def is_unique(self) -> bool:
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return len(self.deltas) == 1
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@cache_readonly
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def is_unique_asi8(self) -> bool:
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return len(self.deltas_asi8) == 1
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def get_freq(self) -> str | None:
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"""
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Find the appropriate frequency string to describe the inferred
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frequency of self.i8values
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Returns
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-------
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str or None
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"""
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if not self.is_monotonic or not self.index._is_unique:
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return None
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delta = self.deltas[0]
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ppd = periods_per_day(self._creso)
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if delta and _is_multiple(delta, ppd):
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return self._infer_daily_rule()
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# Business hourly, maybe. 17: one day / 65: one weekend
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if self.hour_deltas in ([1, 17], [1, 65], [1, 17, 65]):
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return "bh"
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# Possibly intraday frequency. Here we use the
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# original .asi8 values as the modified values
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# will not work around DST transitions. See #8772
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if not self.is_unique_asi8:
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return None
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delta = self.deltas_asi8[0]
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pph = ppd // 24
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ppm = pph // 60
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pps = ppm // 60
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if _is_multiple(delta, pph):
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# Hours
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return _maybe_add_count("h", delta / pph)
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elif _is_multiple(delta, ppm):
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# Minutes
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return _maybe_add_count("min", delta / ppm)
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elif _is_multiple(delta, pps):
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# Seconds
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return _maybe_add_count("s", delta / pps)
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elif _is_multiple(delta, (pps // 1000)):
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# Milliseconds
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return _maybe_add_count("ms", delta / (pps // 1000))
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elif _is_multiple(delta, (pps // 1_000_000)):
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# Microseconds
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return _maybe_add_count("us", delta / (pps // 1_000_000))
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else:
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# Nanoseconds
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return _maybe_add_count("ns", delta)
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@cache_readonly
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def day_deltas(self) -> list[int]:
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ppd = periods_per_day(self._creso)
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return [x / ppd for x in self.deltas]
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@cache_readonly
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def hour_deltas(self) -> list[int]:
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pph = periods_per_day(self._creso) // 24
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return [x / pph for x in self.deltas]
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@cache_readonly
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def fields(self) -> np.ndarray: # structured array of fields
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return build_field_sarray(self.i8values, reso=self._creso)
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@cache_readonly
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def rep_stamp(self) -> Timestamp:
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return Timestamp(self.i8values[0], unit=self.index.unit)
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def month_position_check(self) -> str | None:
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return month_position_check(self.fields, self.index.dayofweek)
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@cache_readonly
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def mdiffs(self) -> npt.NDArray[np.int64]:
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nmonths = self.fields["Y"] * 12 + self.fields["M"]
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return unique_deltas(nmonths.astype("i8"))
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@cache_readonly
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def ydiffs(self) -> npt.NDArray[np.int64]:
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return unique_deltas(self.fields["Y"].astype("i8"))
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def _infer_daily_rule(self) -> str | None:
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annual_rule = self._get_annual_rule()
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if annual_rule:
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nyears = self.ydiffs[0]
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month = MONTH_ALIASES[self.rep_stamp.month]
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alias = f"{annual_rule}-{month}"
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return _maybe_add_count(alias, nyears)
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quarterly_rule = self._get_quarterly_rule()
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if quarterly_rule:
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nquarters = self.mdiffs[0] / 3
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mod_dict = {0: 12, 2: 11, 1: 10}
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month = MONTH_ALIASES[mod_dict[self.rep_stamp.month % 3]]
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alias = f"{quarterly_rule}-{month}"
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return _maybe_add_count(alias, nquarters)
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monthly_rule = self._get_monthly_rule()
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if monthly_rule:
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return _maybe_add_count(monthly_rule, self.mdiffs[0])
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if self.is_unique:
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return self._get_daily_rule()
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if self._is_business_daily():
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return "B"
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wom_rule = self._get_wom_rule()
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if wom_rule:
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return wom_rule
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return None
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def _get_daily_rule(self) -> str | None:
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ppd = periods_per_day(self._creso)
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days = self.deltas[0] / ppd
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if days % 7 == 0:
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# Weekly
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wd = int_to_weekday[self.rep_stamp.weekday()]
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alias = f"W-{wd}"
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return _maybe_add_count(alias, days / 7)
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else:
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return _maybe_add_count("D", days)
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def _get_annual_rule(self) -> str | None:
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if len(self.ydiffs) > 1:
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return None
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if len(unique(self.fields["M"])) > 1:
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return None
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pos_check = self.month_position_check()
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if pos_check is None:
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return None
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else:
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return {"cs": "YS", "bs": "BYS", "ce": "YE", "be": "BYE"}.get(pos_check)
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def _get_quarterly_rule(self) -> str | None:
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if len(self.mdiffs) > 1:
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return None
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if not self.mdiffs[0] % 3 == 0:
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return None
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pos_check = self.month_position_check()
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if pos_check is None:
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return None
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else:
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return {"cs": "QS", "bs": "BQS", "ce": "QE", "be": "BQE"}.get(pos_check)
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def _get_monthly_rule(self) -> str | None:
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if len(self.mdiffs) > 1:
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return None
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pos_check = self.month_position_check()
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if pos_check is None:
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return None
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else:
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return {"cs": "MS", "bs": "BMS", "ce": "ME", "be": "BME"}.get(pos_check)
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def _is_business_daily(self) -> bool:
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# quick check: cannot be business daily
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if self.day_deltas != [1, 3]:
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return False
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# probably business daily, but need to confirm
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first_weekday = self.index[0].weekday()
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shifts = np.diff(self.i8values)
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ppd = periods_per_day(self._creso)
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shifts = np.floor_divide(shifts, ppd)
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weekdays = np.mod(first_weekday + np.cumsum(shifts), 7)
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return bool(
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np.all(
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((weekdays == 0) & (shifts == 3))
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| ((weekdays > 0) & (weekdays <= 4) & (shifts == 1))
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)
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)
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def _get_wom_rule(self) -> str | None:
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weekdays = unique(self.index.weekday)
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if len(weekdays) > 1:
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return None
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week_of_months = unique((self.index.day - 1) // 7)
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# Only attempt to infer up to WOM-4. See #9425
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week_of_months = week_of_months[week_of_months < 4]
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if len(week_of_months) == 0 or len(week_of_months) > 1:
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return None
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# get which week
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week = week_of_months[0] + 1
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wd = int_to_weekday[weekdays[0]]
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return f"WOM-{week}{wd}"
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class _TimedeltaFrequencyInferer(_FrequencyInferer):
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def _infer_daily_rule(self):
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if self.is_unique:
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return self._get_daily_rule()
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def _is_multiple(us, mult: int) -> bool:
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return us % mult == 0
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def _maybe_add_count(base: str, count: float) -> str:
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if count != 1:
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assert count == int(count)
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count = int(count)
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return f"{count}{base}"
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else:
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return base
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# ----------------------------------------------------------------------
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# Frequency comparison
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def is_subperiod(source, target) -> bool:
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"""
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Returns True if downsampling is possible between source and target
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frequencies
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Parameters
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----------
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source : str or DateOffset
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Frequency converting from
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target : str or DateOffset
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Frequency converting to
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Returns
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-------
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bool
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"""
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if target is None or source is None:
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return False
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source = _maybe_coerce_freq(source)
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target = _maybe_coerce_freq(target)
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if _is_annual(target):
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if _is_quarterly(source):
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return _quarter_months_conform(
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get_rule_month(source), get_rule_month(target)
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)
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return source in {"D", "C", "B", "M", "h", "min", "s", "ms", "us", "ns"}
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elif _is_quarterly(target):
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return source in {"D", "C", "B", "M", "h", "min", "s", "ms", "us", "ns"}
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elif _is_monthly(target):
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return source in {"D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
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elif _is_weekly(target):
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return source in {target, "D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
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elif target == "B":
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return source in {"B", "h", "min", "s", "ms", "us", "ns"}
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elif target == "C":
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return source in {"C", "h", "min", "s", "ms", "us", "ns"}
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elif target == "D":
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return source in {"D", "h", "min", "s", "ms", "us", "ns"}
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elif target == "h":
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return source in {"h", "min", "s", "ms", "us", "ns"}
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elif target == "min":
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return source in {"min", "s", "ms", "us", "ns"}
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elif target == "s":
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return source in {"s", "ms", "us", "ns"}
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elif target == "ms":
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return source in {"ms", "us", "ns"}
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elif target == "us":
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return source in {"us", "ns"}
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elif target == "ns":
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return source in {"ns"}
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else:
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return False
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def is_superperiod(source, target) -> bool:
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"""
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Returns True if upsampling is possible between source and target
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frequencies
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Parameters
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----------
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source : str or DateOffset
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Frequency converting from
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target : str or DateOffset
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Frequency converting to
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Returns
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-------
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bool
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"""
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if target is None or source is None:
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return False
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source = _maybe_coerce_freq(source)
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target = _maybe_coerce_freq(target)
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if _is_annual(source):
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if _is_annual(target):
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return get_rule_month(source) == get_rule_month(target)
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if _is_quarterly(target):
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smonth = get_rule_month(source)
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tmonth = get_rule_month(target)
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return _quarter_months_conform(smonth, tmonth)
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return target in {"D", "C", "B", "M", "h", "min", "s", "ms", "us", "ns"}
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elif _is_quarterly(source):
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return target in {"D", "C", "B", "M", "h", "min", "s", "ms", "us", "ns"}
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elif _is_monthly(source):
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return target in {"D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
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elif _is_weekly(source):
|
|
return target in {source, "D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
|
|
elif source == "B":
|
|
return target in {"D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
|
|
elif source == "C":
|
|
return target in {"D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
|
|
elif source == "D":
|
|
return target in {"D", "C", "B", "h", "min", "s", "ms", "us", "ns"}
|
|
elif source == "h":
|
|
return target in {"h", "min", "s", "ms", "us", "ns"}
|
|
elif source == "min":
|
|
return target in {"min", "s", "ms", "us", "ns"}
|
|
elif source == "s":
|
|
return target in {"s", "ms", "us", "ns"}
|
|
elif source == "ms":
|
|
return target in {"ms", "us", "ns"}
|
|
elif source == "us":
|
|
return target in {"us", "ns"}
|
|
elif source == "ns":
|
|
return target in {"ns"}
|
|
else:
|
|
return False
|
|
|
|
|
|
def _maybe_coerce_freq(code) -> str:
|
|
"""we might need to coerce a code to a rule_code
|
|
and uppercase it
|
|
|
|
Parameters
|
|
----------
|
|
source : str or DateOffset
|
|
Frequency converting from
|
|
|
|
Returns
|
|
-------
|
|
str
|
|
"""
|
|
assert code is not None
|
|
if isinstance(code, DateOffset):
|
|
code = freq_to_period_freqstr(1, code.name)
|
|
if code in {"h", "min", "s", "ms", "us", "ns"}:
|
|
return code
|
|
else:
|
|
return code.upper()
|
|
|
|
|
|
def _quarter_months_conform(source: str, target: str) -> bool:
|
|
snum = MONTH_NUMBERS[source]
|
|
tnum = MONTH_NUMBERS[target]
|
|
return snum % 3 == tnum % 3
|
|
|
|
|
|
def _is_annual(rule: str) -> bool:
|
|
rule = rule.upper()
|
|
return rule == "Y" or rule.startswith("Y-")
|
|
|
|
|
|
def _is_quarterly(rule: str) -> bool:
|
|
rule = rule.upper()
|
|
return rule == "Q" or rule.startswith(("Q-", "BQ"))
|
|
|
|
|
|
def _is_monthly(rule: str) -> bool:
|
|
rule = rule.upper()
|
|
return rule in ("M", "BM")
|
|
|
|
|
|
def _is_weekly(rule: str) -> bool:
|
|
rule = rule.upper()
|
|
return rule == "W" or rule.startswith("W-")
|
|
|
|
|
|
__all__ = [
|
|
"Day",
|
|
"get_period_alias",
|
|
"infer_freq",
|
|
"is_subperiod",
|
|
"is_superperiod",
|
|
"to_offset",
|
|
]
|