DEPR: deprecate freq/how arguments to window functions

pandas-dev · jreback · Dec 19, 2015 · Nov 1, 2015 · Nov 21, 2015 · Nov 21, 2015
commit 05eb20f3657c72bbf3caa61409e1c243ec76412f
diff --git a/doc/source/computation.rst b/doc/source/computation.rst
@@ -207,7 +207,6 @@ Window Functions
    functions and are now deprecated and replaced by the corresponding method call.
 
    The deprecation warning will show the new syntax, see an example :ref:`here <whatsnew_0180.window_deprecations>`
-
    You can view the previous documentation
    `here <http://pandas.pydata.org/pandas-docs/version/0.17.1/computation.html#moving-rolling-statistics-moments>`__
 
@@ -244,8 +243,12 @@ accept the following arguments:
 - ``window``: size of moving window
 - ``min_periods``: threshold of non-null data points to require (otherwise
   result is NA)
-- ``freq``: optionally specify a :ref:`frequency string <timeseries.alias>`
-  or :ref:`DateOffset <timeseries.offsets>` to pre-conform the data to.
+
+.. warning::
+
+   The ``freq`` and ``how`` arguments were in the API prior to 0.18.0 changes. These are deprecated in the new API. You can simply resample the input prior to creating a window function.
+
+   For example, instead of ``s.rolling(window=5,freq='D').max()`` to get the max value on a rolling 5 Day window, one could use ``s.resample('D',how='max').rolling(window=5).max()``, which first resamples the data to daily data, then provides a rolling 5 day window.
 
 We can then call methods on these ``rolling`` objects. These return like-indexed objects:
 
@@ -604,8 +607,6 @@ all accept are:
 - ``min_periods``: threshold of non-null data points to require. Defaults to
   minimum needed to compute statistic. No ``NaNs`` will be output once
   ``min_periods`` non-null data points have been seen.
-- ``freq``: optionally specify a :ref:`frequency string <timeseries.alias>`
-  or :ref:`DateOffset <timeseries.offsets>` to pre-conform the data to.
 
 .. note::
 

diff --git a/doc/source/whatsnew/v0.18.0.txt b/doc/source/whatsnew/v0.18.0.txt
@@ -13,6 +13,8 @@ users upgrade to this version.
 
 Highlights include:
 
+- Window functions are now methods on ``.groupby`` like objects, see :ref:`here <whatsnew_0180.moments>`.
+
 Check the :ref:`API Changes <whatsnew_0180.api>` and :ref:`deprecations <whatsnew_0180.deprecations>` before updating.
 
 .. contents:: What's new in v0.18.0
@@ -212,7 +214,7 @@ Deprecations
 
 .. _whatsnew_0180.window_deprecations:
 
-- Function ``pd.rolling_*``, ``pd.expanding_*``, and ``pd.ewm*`` are deprecated and replaced by the corresponding method call. Note that
+- The functions ``pd.rolling_*``, ``pd.expanding_*``, and ``pd.ewm*`` are deprecated and replaced by the corresponding method call. Note that
   the new suggested syntax includes all of the arguments (even if default) (:issue:`11603`)
 
   .. code-block:: python
@@ -237,6 +239,8 @@ Deprecations
              2    0.5
              dtype: float64
 
+- The the ``freq`` and ``how`` arguments to the ``.rolling``, ``.expanding``, and ``.ewm`` (new) functions are deprecated, and will be removed in a future version. (:issue:`11603`)
+
 .. _whatsnew_0180.prior_deprecations:
 
 Removal of prior version deprecations/changes

diff --git a/pandas/core/base.py b/pandas/core/base.py
@@ -462,13 +462,8 @@ def _aggregate_multiple_funcs(self, arg, _level):
                     colg = self._gotitem(obj.name, ndim=1, subset=obj)
                     results.append(colg.aggregate(a))
 
-                    # find a good name, this could be a function that we don't recognize
-                    name = self._is_cython_func(a) or a
-                    if not isinstance(name, compat.string_types):
-                        name = getattr(a,'name',a)
-                    if not isinstance(name, compat.string_types):
-                        name = getattr(a,'__name__',a)
-
+                    # make sure we find a good name
+                    name = com._get_callable_name(a) or a
                     keys.append(name)
                 except (TypeError, DataError):
                     pass

diff --git a/pandas/core/window.py b/pandas/core/window.py
@@ -7,6 +7,7 @@
 """
 from __future__ import division
 
+import warnings
 import numpy as np
 from functools import wraps
 from collections import defaultdict
@@ -39,6 +40,12 @@ class _Window(PandasObject, SelectionMixin):
 
     def __init__(self, obj, window=None, min_periods=None, freq=None, center=False,
                  win_type=None, axis=0):
+
+        if freq is not None:
+            warnings.warn("The freq kw is deprecated and will be removed in a future version. You can resample prior "
+                          "to passing to a window function",
+                          FutureWarning, stacklevel=3)
+
         self.blocks = []
         self.obj = obj
         self.window = window
@@ -298,7 +305,7 @@ def _apply_window(self, mean=True, how=None, **kwargs):
         ----------
         mean : boolean, default True
             If True computes weighted mean, else weighted sum
-        how : string, default to None
+        how : string, default to None (DEPRECATED)
             how to resample
 
         Returns
@@ -378,7 +385,7 @@ def _apply(self, func, window=None, center=None, check_minp=None, how=None, **kw
         window : int/array, default to _get_window()
         center : boolean, default to self.center
         check_minp : function, default to _use_window
-        how : string, default to None
+        how : string, default to None (DEPRECATED)
             how to resample
 
         Returns
@@ -486,21 +493,31 @@ def sum(self):
 
     Parameters
     ----------
-    how : string, default max
+    how : string, default 'max' (DEPRECATED)
     Method for down- or re-sampling""")
-
-    def max(self, how='max'):
+    def max(self, how=None):
+        if how is not None:
+            warnings.warn("The how kw argument is deprecated and removed in a future version. You can resample prior "
+                          "to passing to a window function",
+                          FutureWarning, stacklevel=3)
+        else:
+            how = 'max'
         return self._apply('roll_max', how=how)
 
     _shared_docs['min'] = dedent("""
     %(name)s minimum
 
     Parameters
     ----------
-    how : string, default min
+    how : string, default 'min' (DEPRECATED)
     Method for down- or re-sampling""")
-
-    def min(self, how='min'):
+    def min(self, how=None):
+        if how is not None:
+            warnings.warn("The how kw argument is deprecated and removed in a future version. You can resample prior "
+                          "to passing to a window function",
+                          FutureWarning, stacklevel=3)
+        else:
+            how = 'min'
         return self._apply('roll_min', how=how)
 
     _shared_docs['mean'] = """%(name)s mean"""
@@ -512,10 +529,15 @@ def mean(self):
 
     Parameters
     ----------
-    how : string, default median
+    how : string, default 'median' (DEPRECATED)
     Method for down- or re-sampling""")
-
-    def median(self, how='median'):
+    def median(self, how=None):
+        if how is not None:
+            warnings.warn("The how kw argument is deprecated and removed in a future version. You can resample prior "
+                          "to passing to a window function",
+                          FutureWarning, stacklevel=3)
+        else:
+            how = 'median'
         return self._apply('roll_median_c', how=how)
 
     _shared_docs['std'] = dedent("""
@@ -654,7 +676,7 @@ class Rolling(_Rolling_and_Expanding):
     min_periods : int, default None
         Minimum number of observations in window required to have a value
         (otherwise result is NA).
-    freq : string or DateOffset object, optional (default None)
+    freq : string or DateOffset object, optional (default None) (DEPRECATED)
         Frequency to conform the data to before computing the statistic. Specified
         as a frequency string or DateOffset object.
     center : boolean, default False
@@ -704,14 +726,14 @@ def sum(self):
     @Substitution(name='rolling')
     @Appender(_doc_template)
     @Appender(_shared_docs['max'])
-    def max(self, how='max'):
-        return super(Rolling, self).max(how=how)
+    def max(self, **kwargs):
+        return super(Rolling, self).max(**kwargs)
 
     @Substitution(name='rolling')
     @Appender(_doc_template)
     @Appender(_shared_docs['min'])
-    def min(self, how='min'):
-        return super(Rolling, self).min(how=how)
+    def min(self, **kwargs):
+        return super(Rolling, self).min(**kwargs)
 
     @Substitution(name='rolling')
     @Appender(_doc_template)
@@ -722,8 +744,8 @@ def mean(self):
     @Substitution(name='rolling')
     @Appender(_doc_template)
     @Appender(_shared_docs['median'])
-    def median(self, how='median'):
-        return super(Rolling, self).median(how=how)
+    def median(self, **kwargs):
+        return super(Rolling, self).median(**kwargs)
 
     @Substitution(name='rolling')
     @Appender(_doc_template)
@@ -778,7 +800,7 @@ class Expanding(_Rolling_and_Expanding):
     min_periods : int, default None
         Minimum number of observations in window required to have a value
         (otherwise result is NA).
-    freq : string or DateOffset object, optional (default None)
+    freq : string or DateOffset object, optional (default None) (DEPRECATED)
         Frequency to conform the data to before computing the statistic. Specified
        as a frequency string or DateOffset object.
     center : boolean, default False
@@ -843,14 +865,14 @@ def sum(self):
     @Substitution(name='expanding')
     @Appender(_doc_template)
     @Appender(_shared_docs['max'])
-    def max(self, how='max'):
-        return super(Expanding, self).max(how=how)
+    def max(self, **kwargs):
+        return super(Expanding, self).max(**kwargs)
 
     @Substitution(name='expanding')
     @Appender(_doc_template)
     @Appender(_shared_docs['min'])
-    def min(self, how='min'):
-        return super(Expanding, self).min(how=how)
+    def min(self, **kwargs):
+        return super(Expanding, self).min(**kwargs)
 
     @Substitution(name='expanding')
     @Appender(_doc_template)
@@ -861,8 +883,8 @@ def mean(self):
     @Substitution(name='expanding')
     @Appender(_doc_template)
     @Appender(_shared_docs['median'])
-    def median(self, how='median'):
-        return super(Expanding, self).median(how=how)
+    def median(self, **kwargs):
+        return super(Expanding, self).median(**kwargs)
 
     @Substitution(name='expanding')
     @Appender(_doc_template)
@@ -923,7 +945,7 @@ class EWM(_Rolling):
     min_periods : int, default 0
         Minimum number of observations in window required to have a value
         (otherwise result is NA).
-    freq : None or string alias / date offset object, default=None
+    freq : None or string alias / date offset object, default=None (DEPRECATED)
         Frequency to conform to before computing statistic
     adjust : boolean, default True
         Divide by decaying adjustment factor in beginning periods to account for
@@ -1004,7 +1026,7 @@ def _apply(self, func, how=None, **kwargs):
         Parameters
         ----------
         func : string/callable to apply
-        how : string, default to None
+        how : string, default to None (DEPRECATED)
             how to resample
 
         Returns

diff --git a/pandas/tests/test_window.py b/pandas/tests/test_window.py
@@ -191,6 +191,15 @@ def b(x):
         result = r.aggregate([a,b])
         assert_frame_equal(result, expected)
 
+    def test_preserve_metadata(self):
+        # GH 10565
+        s = Series(np.arange(100), name='foo')
+
+        s2 = s.rolling(30).sum()
+        s3 = s.rolling(20).sum()
+        self.assertEqual(s2.name, 'foo')
+        self.assertEqual(s3.name, 'foo')
+
 class TestDeprecations(Base):
     """ test that we are catching deprecation warnings """
 
@@ -815,10 +824,15 @@ def get_result(obj, window, min_periods=None, freq=None, center=False):
 
             # check via the API calls if name is provided
             if name is not None:
-                return getattr(obj.rolling(window=window,
-                                           min_periods=min_periods,
-                                           freq=freq,
-                                           center=center),name)(**kwargs)
+
+                # catch a freq deprecation warning if freq is provided and not None
+                w = FutureWarning if freq is not None else None
+                with tm.assert_produces_warning(w, check_stacklevel=False):
+                    r = obj.rolling(window=window,
+                                    min_periods=min_periods,
+                                    freq=freq,
+                                    center=center)
+                return getattr(r,name)(**kwargs)
 
             # check via the moments API
             with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
@@ -1002,15 +1016,6 @@ def test_ewma_halflife_arg(self):
             self.assertRaises(Exception, mom.ewma, self.arr, com=9.5, span=20, halflife=50)
             self.assertRaises(Exception, mom.ewma, self.arr)
 
-    def test_moment_preserve_series_name(self):
-        # GH 10565
-        s = Series(np.arange(100), name='foo')
-
-        s2 = s.rolling(30).sum()
-        s3 = s.rolling(20).sum()
-        self.assertEqual(s2.name, 'foo')
-        self.assertEqual(s3.name, 'foo')
-
     def test_ew_empty_arrays(self):
         arr = np.array([], dtype=np.float64)
 
@@ -2133,7 +2138,8 @@ def test_rolling_max_gh6297(self):
         expected = Series([1.0, 2.0, 6.0, 4.0, 5.0],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').max()
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            x = series.rolling(window=1, freq='D').max()
         assert_series_equal(expected, x)
 
     def test_rolling_max_how_resample(self):
@@ -2152,22 +2158,25 @@ def test_rolling_max_how_resample(self):
         expected = Series([0.0, 1.0, 2.0, 3.0, 20.0],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').max()
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            x = series.rolling(window=1, freq='D').max()
         assert_series_equal(expected, x)
 
         # Now specify median (10.0)
         expected = Series([0.0, 1.0, 2.0, 3.0, 10.0],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').max(how='median')
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            x = series.rolling(window=1, freq='D').max(how='median')
         assert_series_equal(expected, x)
 
         # Now specify mean (4+10+20)/3
         v = (4.0+10.0+20.0)/3.0
         expected = Series([0.0, 1.0, 2.0, 3.0, v],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').max(how='mean')
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            x = series.rolling(window=1, freq='D').max(how='mean')
         assert_series_equal(expected, x)
 
 
@@ -2187,8 +2196,9 @@ def test_rolling_min_how_resample(self):
         expected = Series([0.0, 1.0, 2.0, 3.0, 4.0],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').min()
-        assert_series_equal(expected, x)
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            r = series.rolling(window=1, freq='D')
+        assert_series_equal(expected, r.min())
 
     def test_rolling_median_how_resample(self):
 
@@ -2206,14 +2216,15 @@ def test_rolling_median_how_resample(self):
         expected = Series([0.0, 1.0, 2.0, 3.0, 10],
                           index=[datetime(1975, 1, i, 0)
                                  for i in range(1, 6)])
-        x = series.rolling(window=1, freq='D').median()
+        with tm.assert_produces_warning(FutureWarning, check_stacklevel=False):
+            x = series.rolling(window=1, freq='D').median()
         assert_series_equal(expected, x)
 
     def test_rolling_median_memory_error(self):
         # GH11722
         n = 20000
-        mom.rolling_median(Series(np.random.randn(n)), window=2, center=False)
-        mom.rolling_median(Series(np.random.randn(n)), window=2, center=False)
+        Series(np.random.randn(n)).rolling(window=2, center=False).median()
+        Series(np.random.randn(n)).rolling(window=2, center=False).median()
 
 if __name__ == '__main__':
     import nose