In [171]: s = pd.Series(range(3))
In [172]: s.rolling(-1) # doesn't raise
Out[172]: Rolling [window=-1,center=False,axis=0]
In [173]: s.rolling(-1).mean() # Odd, indirect error
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
<ipython-input-173-cda5b8dd0812> in <module>()
----> 1 s.rolling(-1).mean()
/home/mike/modernpandas/local/lib/python2.7/site-packages/pandas/core/window.pyc in mean(self, **kwargs)
885 @Appender(_shared_docs['mean'])
886 def mean(self, **kwargs):
--> 887 return super(Rolling, self).mean(**kwargs)
888
889 @Substitution(name='rolling')
/home/mike/modernpandas/local/lib/python2.7/site-packages/pandas/core/window.pyc in mean(self, **kwargs)
651
652 def mean(self, **kwargs):
--> 653 return self._apply('roll_mean', 'mean', **kwargs)
654
655 _shared_docs['median'] = dedent("""
/home/mike/modernpandas/local/lib/python2.7/site-packages/pandas/core/window.pyc in _apply(self, func, name, window, center, check_minp, how, **kwargs)
558 result = np.apply_along_axis(calc, self.axis, values)
559 else:
--> 560 result = calc(values)
561
562 if center:
/home/mike/modernpandas/local/lib/python2.7/site-packages/pandas/core/window.pyc in calc(x)
553
554 def calc(x):
--> 555 return func(x, window, min_periods=self.min_periods)
556
557 if values.ndim > 1:
/home/mike/modernpandas/local/lib/python2.7/site-packages/pandas/core/window.pyc in func(arg, window, min_periods)
540 # GH #12373: rolling functions error on float32 data
541 return cfunc(com._ensure_float64(arg),
--> 542 window, minp, **kwargs)
543
544 # calculation function
pandas/algos.pyx in pandas.algos.roll_mean (pandas/algos.c:28921)()
pandas/algos.pyx in pandas.algos._check_minp (pandas/algos.c:19103)()
ValueError: min_periods must be >= 0
In [174]: pd.Series([]).rolling(-1).mean() # Never raises
Out[174]: Series([], dtype: float64)
In [175]: pd.show_versions()
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.6.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-71-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
pandas: 0.18.1
nose: 1.3.7
pip: 8.0.2
setuptools: 20.1.1
Cython: 0.24
numpy: 1.11.0
scipy: 0.17.1
statsmodels: 0.6.1
xarray: None
IPython: 4.1.1
sphinx: None
patsy: 0.4.1
dateutil: 2.5.3
pytz: 2016.4
blosc: 1.3.2
bottleneck: None
tables: 3.2.2
numexpr: 2.6.0
matplotlib: 1.5.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.8
boto: 2.40.0
pandas_datareader: None