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PODataFrame.groupby(TimeGrouper="d"): Invalid length for values or for binner
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copied!<p>I am trying to build groups of my data using the groupby function of pandas over a DataFrame with a DateTimeIndex. Using pd.TimeGrouper, I want to group by day.</p> <p>When I define this DataFrame, the below operation <code>n.groupby(pd.TimeGrouper("d"))</code> does not work.</p> <pre><code>n = pd.DataFrame( {"value": [5462,5462,3185]}, index=[pd.to_datetime("2013-10-13 19:03:54"), pd.to_datetime("2013-10-12 19:03:54"), pd.to_datetime("2013-10-11 13:19:23")]) </code></pre> <p>Error:</p> <pre><code>n.groupby(pd.TimeGrouper("d")) --------------------------------------------------------------------------- ValueError Traceback (most recent call last) <ipython-input-248-120eaa65b064> in <module>() ----> 1 n.groupby(pd.TimeGrouper("d")) \lib\site-packages\pandas\core\generic.pyc in groupby(self, by, axis, level, as_index, sort, group_keys, squeeze) 184 return groupby(self, by, axis=axis, level=level, as_index=as_index, 185 sort=sort, group_keys=group_keys, --> 186 squeeze=squeeze) 187 188 def asfreq(self, freq, method=None, how=None, normalize=False): \lib\site-packages\pandas\core\groupby.pyc in groupby(obj, by, **kwds) 531 raise TypeError('invalid type: %s' % type(obj)) 532 --> 533 return klass(obj, by, **kwds) 534 535 \lib\site-packages\pandas\core\groupby.pyc in __init__(self, obj, keys, axis, level, grouper, exclusions, selection, as_index, sort, group_keys, squeeze) 195 if grouper is None: 196 grouper, exclusions = _get_grouper(obj, keys, axis=axis, --> 197 level=level, sort=sort) 198 199 self.grouper = grouper \lib\site-packages\pandas\core\groupby.pyc in _get_grouper(obj, key, axis, level, sort) 1268 1269 if isinstance(key, CustomGrouper): -> 1270 gpr = key.get_grouper(obj) 1271 return gpr, [] 1272 elif isinstance(key, Grouper): \lib\site-packages\pandas\tseries\resample.pyc in get_grouper(self, obj) 106 def get_grouper(self, obj): 107 # Only return grouper --> 108 return self._get_time_grouper(obj)[1] 109 110 def _get_time_grouper(self, obj): \lib\site-packages\pandas\tseries\resample.pyc in _get_time_grouper(self, obj) 112 113 if self.kind is None or self.kind == 'timestamp': --> 114 binner, bins, binlabels = self._get_time_bins(axis) 115 else: 116 binner, bins, binlabels = self._get_time_period_bins(axis) \lib\site-packages\pandas\tseries\resample.pyc in _get_time_bins(self, axis) 146 147 # general version, knowing nothing about relative frequencies --> 148 bins = lib.generate_bins_dt64(ax_values, bin_edges, self.closed) 149 150 if self.closed == 'right': \lib\site-packages\pandas\lib.pyd in pandas.lib.generate_bins_dt64 (pandas\lib.c:16139)() ValueError: Invalid length for values or for binner </code></pre> <p>Surprisingly, when I define the DataFrame like below, it works just fine. Notice that I changed the last day to be 2013-10-12 instead of 2013-10-11.</p> <pre><code>n = pd.DataFrame( {"value": [5462,5462,3185]}, index=[pd.to_datetime("2013-10-13 19:03:54"), pd.to_datetime("2013-10-13 19:03:54"), pd.to_datetime("2013-10-12 13:19:23")]) </code></pre> <p>In this case I get a correct group object:</p> <pre><code>n.groupby(pd.TimeGrouper("d")) <pandas.core.groupby.DataFrameGroupBy object at 0x000000000A3D84E0> </code></pre> <p>I already looked up some of the core functions of pandas in the source code, but I am not sure whether this is a bug or whether I just do not know how to use the function properly.</p> <p>Notice also that aggregating on month works just fine.</p> <p>Thank you for your help.</p>

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