He estado siguiendo 'python para análisis de datos'. En la pág. 345, llega a este código para trazar los retornos en una variedad de acciones. Sin embargo, la función de trazado no funciona para mí. Me sale el objeto FigureCanvasAgg 'no tiene atributo' invalidar '?

names = ['AAPL','MSFT', 'DELL', 'MS', 'BAC', 'C'] #goog and SF did not work
def get_px(stock, start, end):
    return web.get_data_yahoo(stock, start, end)['Adj Close']
px = pd.DataFrame({n: get_px(n, '1/1/2009', '6/1/2012') for n in names})

#fillna method pad uses last valid observation to fill
px = px.asfreq('B').fillna(method='pad')
rets = px.pct_change()
df2 = ((1 + rets).cumprod() - 1)

df2.ix[0] = 1

df2.plot()

ACTUALIZACIÓN: rastreo completo

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-122-df192c0432be> in <module>()
      6 df2.ix[0] = 1
      7 
----> 8 df2.plot()

//anaconda/lib/python2.7/site-packages/pandas/tools/plotting.pyc in plot_frame(frame, x, y, subplots, sharex, sharey, use_index, figsize, grid, legend, rot, ax, style, title, xlim, ylim, logx, logy, xticks, yticks, kind, sort_columns, fontsize, secondary_y, **kwds)
   1634                      logy=logy, sort_columns=sort_columns,
   1635                      secondary_y=secondary_y, **kwds)
-> 1636     plot_obj.generate()
   1637     plot_obj.draw()
   1638     if subplots:

//anaconda/lib/python2.7/site-packages/pandas/tools/plotting.pyc in generate(self)
    854         self._compute_plot_data()
    855         self._setup_subplots()
--> 856         self._make_plot()
    857         self._post_plot_logic()
    858         self._adorn_subplots()

//anaconda/lib/python2.7/site-packages/pandas/tools/plotting.pyc in _make_plot(self)
   1238         if not self.x_compat and self.use_index and self._use_dynamic_x():
   1239             data = self._maybe_convert_index(self.data)
-> 1240             self._make_ts_plot(data, **self.kwds)
   1241         else:
   1242             lines = []

//anaconda/lib/python2.7/site-packages/pandas/tools/plotting.pyc in _make_ts_plot(self, data, **kwargs)
   1319                 self._maybe_add_color(colors, kwds, style, i)
   1320 
-> 1321                 _plot(data[col], i, ax, label, style, **kwds)
   1322 
   1323         self._make_legend(lines, labels)

//anaconda/lib/python2.7/site-packages/pandas/tools/plotting.pyc in _plot(data, col_num, ax, label, style, **kwds)
   1293         def _plot(data, col_num, ax, label, style, **kwds):
   1294             newlines = tsplot(data, plotf, ax=ax, label=label,
-> 1295                                 style=style, **kwds)
   1296             ax.grid(self.grid)
   1297             lines.append(newlines[0])

//anaconda/lib/python2.7/site-packages/pandas/tseries/plotting.pyc in tsplot(series, plotf, **kwargs)
     79 
     80     # set date formatter, locators and rescale limits
---> 81     format_dateaxis(ax, ax.freq)
     82     left, right = _get_xlim(ax.get_lines())
     83     ax.set_xlim(left, right)

//anaconda/lib/python2.7/site-packages/pandas/tseries/plotting.pyc in format_dateaxis(subplot, freq)
    258     subplot.xaxis.set_major_formatter(majformatter)
    259     subplot.xaxis.set_minor_formatter(minformatter)
--> 260     pylab.draw_if_interactive()

//anaconda/lib/python2.7/site-packages/IPython/utils/decorators.pyc in wrapper(*args, **kw)
     41     def wrapper(*args,**kw):
     42         wrapper.called = False
---> 43         out = func(*args,**kw)
     44         wrapper.called = True
     45         return out

//anaconda/lib/python2.7/site-packages/matplotlib/backends/backend_macosx.pyc in draw_if_interactive()
    227         figManager =  Gcf.get_active()
    228         if figManager is not None:
--> 229             figManager.canvas.invalidate()
    230 
    231 

AttributeError: 'FigureCanvasAgg' object has no attribute 'invalidate'