anyone know pandas ? Don't understand error: NotImplementedError...

[someone]

Hi,

Here's my script (from 
http://brenda.moon.net.au/category/data-visualisation/:

============================
#!/usr/bin/python

import pandas
import datetime
import numpy

datesList = [datetime.date(2011,12,1), \
              datetime.date(2011,12,2), \
              datetime.date(2011,12,3), \
              datetime.date(2011,12,10)]

countsList = numpy.random.randn(len(datesList))
startData = datetime.datetime(2011,12,3)
endData = datetime.datetime(2011,12,8)

def convertListPairToTimeSeries(dList, cList):
     # my dateList had date objects, so convert back to datetime objects
     dListDT = [datetime.datetime.combine(x, datetime.time()) for x in 
dList]
     # found that NaN didn't work if the cList contained int data
     cListL = [float(x) for x in cList]
     #  create the index from the datestimes list
     indx = pandas.Index(dListDT)
     #  create the timeseries
     ts = pandas.Series(cListL, index=indx)
     # fill in missing days
     ts = ts.asfreq(pandas.datetools.DateOffset())
     return ts

print "\nOriginal datesList list:\n", datesList
tSeries = convertListPairToTimeSeries(datesList, countsList)
print "\nPandas timeseries:\n", tSeries

# use slicing to change length of data
tSeriesSlice = tSeries.ix[startData:endData]
print "\nPandas timeseries sliced between", startData.date(), \
   "and", endData.date(), ":\n", tSeriesSlice

# use truncate instead of slicing to change length of data
tSeriesTruncate = tSeries.truncate(before=startData, after=endData)
print "\nPandas timeseries truncated between", startData.date(), \
   "and", endData.date(), ":\n", tSeriesTruncate

# my data had lots of gaps that were actually 0 values, not missing data
# So I used this to fix the NaN outside the known outage
startOutage = datetime.datetime(2011,12,7)
endOutage = datetime.datetime(2011,12,8)
tsFilled = tSeries.fillna(0)
# set the known outage values back to NAN
tsFilled.ix[startOutage:endOutage] = numpy.NAN
print "\nPandas timeseries NaN reset to 0 outside known outage between", \
   startOutage.date(), "and", endOutage.date(), ":\n", tsFilled

print "\nPandas series.tail(1) and series.head(1) are handy for " +\
   "checking ends of list:\n", tsFilled.head(1), tsFilled.tail(1)
print

tsFilled.plot(); # <======  NotImplementedError...!!!
============================


If I run it, I get:
--------------------
...
...
..
2011-12-09    0.000000
2011-12-10    1.431665
Freq: <1 DateOffset>

Pandas series.tail(1) and series.head(1) are handy for checking ends of 
list:
2011-12-01   -0.969533
Freq: <1 DateOffset> 2011-12-10    1.431665
Freq: <1 DateOffset>

Traceback (most recent call last):
   File "./pandas_example.py", line 57, in <module>
     tsFilled.plot();
   File "/usr/lib/pymodules/python2.7/pandas/tools/plotting.py", line 
985, in plot_series
     plot_obj.generate()
   File "/usr/lib/pymodules/python2.7/pandas/tools/plotting.py", line 
376, in generate
     self._make_plot()
   File "/usr/lib/pymodules/python2.7/pandas/tools/plotting.py", line 
623, in _make_plot
     if self.use_index and self._use_dynamic_x():
   File "/usr/lib/pymodules/python2.7/pandas/tools/plotting.py", line 
619, in _use_dynamic_x
     return (freq is not None) and self._is_dynamic_freq(freq)
   File "/usr/lib/pymodules/python2.7/pandas/tools/plotting.py", line 
602, in _is_dynamic_freq
     freq = freq.rule_code
   File "/usr/lib/pymodules/python2.7/pandas/tseries/offsets.py", line 
214, in rule_code
     raise NotImplementedError
NotImplementedError
--------------------

Can anyone tell why this error appears and how to fix it?