I'm having a pandas Series
object filled with decimal numbers of dtype Decimal. I'd like to use the new pandas 0.8 function to resample the decimal time series like this:
resampled = ts.resample('D', how = 'mean')
When trying this i get an "GroupByError: No numeric types to aggregate" error. I assume the problem is that np.mean is used internaly to resample the values and np.mean expects floats instead of Decimals.
Thanks to the help of this forum i managed to solve a similar question using groupBy and the apply function but i would love to also use the cool resample function.
How use the mean method on a pandas TimeSeries with Decimal type values?
Any idea how to solve this?
Here is the complete ipython session creating the error:
In [37]: from decimal import Decimal
In [38]: from pandas import *
In [39]: rng = date_range('1.1.2012',periods=48, freq='H')
In [40]: rnd = np.random.randn(len(rng))
In [41]: rnd_dec = [Decimal(x) for x in rnd]
In [42]: ts = Series(rnd_dec, index=rng)
In [43]: ts[0:3]
Out[43]:
2012-01-01 00:00:00 -0.1020591335576267189022559023214853368699550628
2012-01-01 01:00:00 0.99245713975437366283216533702216111123561859130
2012-01-01 02:00:00 1.80080710727195758558139004890108481049537658691
Freq: H
In [44]: type(ts[0])
Out[44]: decimal.Decimal
In [45]: ts.resample('D', how = 'mean')
---------------------------------------------------------------------------
GroupByError Traceback (most recent call last)
C:\Users\THM\Documents\Python\<ipython-input-45-09c898403ddd> in <module>()
----> 1 ts.resample('D', how = 'mean')
C:\Python27\lib\site-packages\pandas\core\generic.pyc in resample(self, rule, how, axis, fill_method, closed, label, convention, kind, loffset, l
imit, base)
187 fill_method=fill_method, convention=convention,
188 limit=limit, base=base)
--> 189 return sampler.resample(self)
190
191 def first(self, offset):
C:\Python27\lib\site-packages\pandas\tseries\resample.pyc in resample(self, obj)
65
66 if isinstance(axis, DatetimeIndex):
---> 67 rs = self._resample_timestamps(obj)
68 elif isinstance(axis, PeriodIndex):
69 offset = to_offset(self.freq)
C:\Python27\lib\site-packages\pandas\tseries\resample.pyc in _resample_timestamps(self, obj)
184 if len(grouper.binlabels) < len(axlabels) or self.how is not None:
185 grouped = obj.groupby(grouper, axis=self.axis)
--> 186 result = grouped.aggregate(self._agg_method)
187 else:
188 # upsampling shortcut
C:\Python27\lib\site-packages\pandas\core\groupby.pyc in aggregate(self, func_or_funcs, *args, **kwargs)
1215 """
1216 if isinstance(func_or_funcs, basestring):
-> 1217 return getattr(self, func_or_funcs)(*args, **kwargs)
1218
1219 if hasattr(func_or_funcs,'__iter__'):
C:\Python27\lib\site-packages\pandas\core\groupby.pyc in mean(self)
290 """
291 try:
--> 292 return self._cython_agg_general('mean')
293 except GroupByError:
294 raise
C:\Python27\lib\site-packages\pandas\core\groupby.pyc in _cython_agg_general(self, how)
376
377 if len(output) == 0:
--> 378 raise GroupByError('No numeric types to aggregate')
379
380 return self._wrap_aggregated_output(output, names)
GroupByError: No numeric types to aggregate
Any help is appreciated. Thanks, Thomas
Resample Pandas time-series dataThe resample() function is used to resample time-series data. Convenience method for frequency conversion and resampling of time series. Object must have a datetime-like index (DatetimeIndex, PeriodIndex, or TimedeltaIndex), or pass datetime-like values to the on or level keyword.
Use pandas.display. float_format to "{:,. 2f}". format to display float values to two decimal places.
I found the answer by myself. It is possible to provide a function to the 'how' argument of resample:
f = lambda x: Decimal(np.mean(x))
ts.resample('D', how = f)
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