Source code for dask.dataframe.rolling

import datetime
import inspect
from numbers import Integral

import pandas as pd
from pandas.api.types import is_datetime64_any_dtype
from pandas.core.window import Rolling as pd_Rolling

from ..base import tokenize
from ..highlevelgraph import HighLevelGraph
from ..utils import M, derived_from, funcname, has_keyword
from . import methods
from .core import _emulate
from .utils import make_meta


def overlap_chunk(
    func, prev_part, current_part, next_part, before, after, args, kwargs
):

    msg = (
        "Partition size is less than overlapping "
        "window size. Try using ``df.repartition`` "
        "to increase the partition size."
    )

    if prev_part is not None and isinstance(before, Integral):
        if prev_part.shape[0] != before:
            raise NotImplementedError(msg)

    if next_part is not None and isinstance(after, Integral):
        if next_part.shape[0] != after:
            raise NotImplementedError(msg)

    parts = [p for p in (prev_part, current_part, next_part) if p is not None]
    combined = methods.concat(parts)
    out = func(combined, *args, **kwargs)
    if prev_part is None:
        before = None
    if isinstance(before, datetime.timedelta):
        before = len(prev_part)

    expansion = None
    if combined.shape[0] != 0:
        expansion = out.shape[0] // combined.shape[0]
    if before and expansion:
        before *= expansion
    if next_part is None:
        return out.iloc[before:]
    if isinstance(after, datetime.timedelta):
        after = len(next_part)
    if after and expansion:
        after *= expansion
    return out.iloc[before:-after]


[docs]def map_overlap(func, df, before, after, *args, **kwargs): """Apply a function to each partition, sharing rows with adjacent partitions. Parameters ---------- func : function Function applied to each partition. df : dd.DataFrame, dd.Series before : int or timedelta The rows to prepend to partition ``i`` from the end of partition ``i - 1``. after : int or timedelta The rows to append to partition ``i`` from the beginning of partition ``i + 1``. args, kwargs : Arguments and keywords to pass to the function. The partition will be the first argument, and these will be passed *after*. See Also -------- dd.DataFrame.map_overlap """ if isinstance(before, datetime.timedelta) or isinstance(after, datetime.timedelta): if not is_datetime64_any_dtype(df.index._meta_nonempty.inferred_type): raise TypeError( "Must have a `DatetimeIndex` when using string offset " "for `before` and `after`" ) else: if not ( isinstance(before, Integral) and before >= 0 and isinstance(after, Integral) and after >= 0 ): raise ValueError("before and after must be positive integers") if "token" in kwargs: func_name = kwargs.pop("token") token = tokenize(df, before, after, *args, **kwargs) else: func_name = "overlap-" + funcname(func) token = tokenize(func, df, before, after, *args, **kwargs) if "meta" in kwargs: meta = kwargs.pop("meta") else: meta = _emulate(func, df, *args, **kwargs) meta = make_meta(meta, index=df._meta.index, parent_meta=df._meta) name = f"{func_name}-{token}" name_a = "overlap-prepend-" + tokenize(df, before) name_b = "overlap-append-" + tokenize(df, after) df_name = df._name dsk = {} timedelta_partition_message = ( "Partition size is less than specified window. " "Try using ``df.repartition`` to increase the partition size" ) if before and isinstance(before, Integral): prevs = [None] for i in range(df.npartitions - 1): key = (name_a, i) dsk[key] = (M.tail, (df_name, i), before) prevs.append(key) elif isinstance(before, datetime.timedelta): # Assumes monotonic (increasing?) index divs = pd.Series(df.divisions) deltas = divs.diff().iloc[1:-1] # In the first case window-size is larger than at least one partition, thus it is # necessary to calculate how many partitions must be used for each rolling task. # Otherwise, these calculations can be skipped (faster) if (before > deltas).any(): pt_z = divs[0] prevs = [None] for i in range(df.npartitions - 1): # Select all indexes of relevant partitions between the current partition and # the partition with the highest division outside the rolling window (before) pt_i = divs[i + 1] # lower-bound the search to the first division lb = max(pt_i - before, pt_z) first, j = divs[i], i while first > lb and j > 0: first = first - deltas[j] j = j - 1 key = (name_a, i) dsk[key] = ( _tail_timedelta, [(df_name, k) for k in range(j, i + 1)], (df_name, i + 1), before, ) prevs.append(key) else: prevs = [None] for i in range(df.npartitions - 1): key = (name_a, i) dsk[key] = ( _tail_timedelta, [(df_name, i)], (df_name, i + 1), before, ) prevs.append(key) else: prevs = [None] * df.npartitions if after and isinstance(after, Integral): nexts = [] for i in range(1, df.npartitions): key = (name_b, i) dsk[key] = (M.head, (df_name, i), after) nexts.append(key) nexts.append(None) elif isinstance(after, datetime.timedelta): # TODO: Do we have a use-case for this? Pandas doesn't allow negative rolling windows deltas = pd.Series(df.divisions).diff().iloc[1:-1] if (after > deltas).any(): raise ValueError(timedelta_partition_message) nexts = [] for i in range(1, df.npartitions): key = (name_b, i) dsk[key] = (_head_timedelta, (df_name, i - 0), (df_name, i), after) nexts.append(key) nexts.append(None) else: nexts = [None] * df.npartitions for i, (prev, current, next) in enumerate(zip(prevs, df.__dask_keys__(), nexts)): dsk[(name, i)] = ( overlap_chunk, func, prev, current, next, before, after, args, kwargs, ) graph = HighLevelGraph.from_collections(name, dsk, dependencies=[df]) return df._constructor(graph, name, meta, df.divisions)
def _head_timedelta(current, next_, after): """Return rows of ``next_`` whose index is before the last observation in ``current`` + ``after``. Parameters ---------- current : DataFrame next_ : DataFrame after : timedelta Returns ------- overlapped : DataFrame """ return next_[next_.index < (current.index.max() + after)] def _tail_timedelta(prevs, current, before): """Return the concatenated rows of each dataframe in ``prevs`` whose index is after the first observation in ``current`` - ``before``. Parameters ---------- current : DataFrame prevs : list of DataFrame objects before : timedelta Returns ------- overlapped : DataFrame """ selected = methods.concat( [prev[prev.index > (current.index.min() - before)] for prev in prevs] ) return selected def pandas_rolling_method(df, rolling_kwargs, name, *args, **kwargs): rolling = df.rolling(**rolling_kwargs) return getattr(rolling, name)(*args, **kwargs) class Rolling: """Provides rolling window calculations.""" def __init__( self, obj, window=None, min_periods=None, center=False, win_type=None, axis=0 ): self.obj = obj # dataframe or series self.window = window self.min_periods = min_periods self.center = center self.axis = axis self.win_type = win_type # Allow pandas to raise if appropriate obj._meta.rolling(**self._rolling_kwargs()) # Using .rolling(window='2s'), pandas will convert the # offset str to a window in nanoseconds. But pandas doesn't # accept the integer window with win_type='freq', so we store # that information here. # See https://github.com/pandas-dev/pandas/issues/15969 self._win_type = None if isinstance(self.window, int) else "freq" def _rolling_kwargs(self): return { "window": self.window, "min_periods": self.min_periods, "center": self.center, "win_type": self.win_type, "axis": self.axis, } @property def _has_single_partition(self): """ Indicator for whether the object has a single partition (True) or multiple (False). """ return ( self.axis in (1, "columns") or (isinstance(self.window, Integral) and self.window <= 1) or self.obj.npartitions == 1 ) def _call_method(self, method_name, *args, **kwargs): rolling_kwargs = self._rolling_kwargs() meta = pandas_rolling_method( self.obj._meta_nonempty, rolling_kwargs, method_name, *args, **kwargs ) if self._has_single_partition: # There's no overlap just use map_partitions return self.obj.map_partitions( pandas_rolling_method, rolling_kwargs, method_name, *args, token=method_name, meta=meta, **kwargs, ) # Convert window to overlap if self.center: before = self.window // 2 after = self.window - before - 1 elif self._win_type == "freq": before = pd.Timedelta(self.window) after = 0 else: before = self.window - 1 after = 0 return map_overlap( pandas_rolling_method, self.obj, before, after, rolling_kwargs, method_name, *args, token=method_name, meta=meta, **kwargs, )
[docs] @derived_from(pd_Rolling) def count(self): return self._call_method("count")
@derived_from(pd_Rolling) def cov(self): return self._call_method("cov")
[docs] @derived_from(pd_Rolling) def sum(self): return self._call_method("sum")
[docs] @derived_from(pd_Rolling) def mean(self): return self._call_method("mean")
[docs] @derived_from(pd_Rolling) def median(self): return self._call_method("median")
[docs] @derived_from(pd_Rolling) def min(self): return self._call_method("min")
[docs] @derived_from(pd_Rolling) def max(self): return self._call_method("max")
[docs] @derived_from(pd_Rolling) def std(self, ddof=1): return self._call_method("std", ddof=1)
[docs] @derived_from(pd_Rolling) def var(self, ddof=1): return self._call_method("var", ddof=1)
[docs] @derived_from(pd_Rolling) def skew(self): return self._call_method("skew")
[docs] @derived_from(pd_Rolling) def kurt(self): return self._call_method("kurt")
[docs] @derived_from(pd_Rolling) def quantile(self, quantile): return self._call_method("quantile", quantile)
[docs] @derived_from(pd_Rolling) def apply( self, func, raw=None, engine="cython", engine_kwargs=None, args=None, kwargs=None, ): compat_kwargs = {} kwargs = kwargs or {} args = args or () meta = self.obj._meta.rolling(0) if has_keyword(meta.apply, "engine"): # PANDAS_GT_100 compat_kwargs = dict(engine=engine, engine_kwargs=engine_kwargs) if raw is None: # PANDAS_GT_100: The default changed from None to False raw = inspect.signature(meta.apply).parameters["raw"] return self._call_method( "apply", func, raw=raw, args=args, kwargs=kwargs, **compat_kwargs )
@derived_from(pd_Rolling) def aggregate(self, func, args=(), kwargs={}, **kwds): return self._call_method("agg", func, args=args, kwargs=kwargs, **kwds) agg = aggregate def __repr__(self): def order(item): k, v = item _order = { "window": 0, "min_periods": 1, "center": 2, "win_type": 3, "axis": 4, } return _order[k] rolling_kwargs = self._rolling_kwargs() rolling_kwargs["window"] = self.window rolling_kwargs["win_type"] = self._win_type return "Rolling [{}]".format( ",".join( f"{k}={v}" for k, v in sorted(rolling_kwargs.items(), key=order) if v is not None ) )