title: how to plot histograms from dataframes in pandas
body: <p>I have a simple dataframe in pandas that has two numeric columns. I want to make a histogram out of the columns using matplotlib through pandas. The example below does not work:</p>
  
  <pre><code>In [6]: pandas.__version__
  Out[6]: '0.14.1'
  
  In [7]: df
  Out[7]: 
     a   b
  0  1  20
  1  2  40
  2  3  30
  3  4  30
  4  4   3
  5  3   5
  
  In [8]: df.plot(kind="hist")
  ---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-8-4f53176a4683&gt; in &lt;module&gt;()
  ----&gt; 1 df.plot(kind="hist")
  
  /software/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)
     2095         klass = _plot_klass[kind]
     2096     else:
  -&gt; 2097         raise ValueError('Invalid chart type given %s' % kind)
     2098 
     2099     if kind in _dataframe_kinds:
  
  ValueError: Invalid chart type given hist
  </code></pre>
  
  <p>why does it say invalid chart type? the columns are numeric and can be made into histograms.</p>