title: pandas plot time series ['numpy.ndarray' object has no attribute 'find']
body: <p>I have the following code attempting to plot a timeseries. Note, I drop the second column because it's not relevant. And I drop the first and last rows.</p>
  
  <pre><code>import pandas as pd
  
  activity = pd.read_csv('activity.csv', index_col=2)
  activity = activity.ix[1:-1] #drop first and last rows due to invalid data
  series = activity['activity']
  series.plot()
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>---------------------------------------------------------------------------
  AttributeError                            Traceback (most recent call last)
  &lt;ipython-input-10-36df40c11065&gt; in &lt;module&gt;()
  ----&gt; 1 series.plot()
  
  .../pandas/tools/plotting.pyc in plot_series(series, label, kind, use_index,
                                               rot, xticks, yticks, xlim, ylim,
                                               ax, style, grid, logy,
                                               secondary_y, **kwds)
     1326                      secondary_y=secondary_y, **kwds)
     1327 
  -&gt; 1328     plot_obj.generate()
     1329     plot_obj.draw()
     1330 
  
  .../pandas/tools/plotting.pyc in generate(self)
      573         self._compute_plot_data()
      574         self._setup_subplots()
  --&gt; 575         self._make_plot()
      576         self._post_plot_logic()
      577         self._adorn_subplots()
  
  .../pandas/tools/plotting.pyc in _make_plot(self)
      916                     args = (ax, x, y, style)
      917 
  --&gt; 918                 newline = plotf(*args, **kwds)[0]
      919                 lines.append(newline)
      920                 leg_label = label
  
  .../matplotlib/axes.pyc in plot(self, *args, **kwargs)
     3991         lines = []
     3992 
  -&gt; 3993         for line in self._get_lines(*args, **kwargs):
     3994             self.add_line(line)
     3995             lines.append(line)
  
  .../matplotlib&gt;/axes.pyc in _grab_next_args(self, *args, **kwargs)
      328                 return
      329             if len(remaining) &lt;= 3:
  --&gt; 330                 for seg in self._plot_args(remaining, kwargs):
      331                     yield seg
      332                 return
  
  .../matplotlib/axes.pyc in _plot_args(self, tup, kwargs)
      287         ret = []
      288         if len(tup) &gt; 1 and is_string_like(tup[-1]):
  --&gt; 289             linestyle, marker, color = _process_plot_format(tup[-1])
      290             tup = tup[:-1]
      291         elif len(tup) == 3:
  
  .../matplotlib/axes.pyc in _process_plot_format(fmt)
       94     # handle the multi char special cases and strip them from the
       95     # string
  ---&gt; 96     if fmt.find('--')&gt;=0:
       97         linestyle = '--'
       98         fmt = fmt.replace('--', '')
  
  AttributeError: 'numpy.ndarray' object has no attribute 'find'
  </code></pre>
  
  <p>If I try it with a small dataset such as:</p>
  
  <pre><code>target, weekday, timestamp
  0, Sat, 08 Dec 2012 16:26:26:625000
  0, Sat, 08 Dec 2012 16:26:27:625000
  0, Sat, 08 Dec 2012 16:26:28:625000
  0, Sat, 08 Dec 2012 16:26:29:625000
  1, Sat, 08 Dec 2012 16:26:30:625000
  2, Sat, 08 Dec 2012 16:26:31:625000
  0, Sat, 08 Dec 2012 16:26:32:625000
  0, Sat, 08 Dec 2012 16:26:33:625000
  1, Sat, 08 Dec 2012 16:26:34:625000
  2, Sat, 08 Dec 2012 16:26:35:625000
  </code></pre>
  
  <p>it works, but not on my full dataset. <a href="https://dl.dropbox.com/u/60861504/activity.csv" rel="nofollow">https://dl.dropbox.com/u/60861504/activity.csv</a>
  Also I tried it with the first 10 items from my dataset and got the same error, but if I assign one value manually <code>series[10] = 5</code> the plot shows up. I'm stumped.</p>