title: Holoviews: How to plot DataFrame with time index
body: <p>I am trying to plot a Pandas DataFrame (more pecisely one column of it) with a timestamped index using Holoviews DFrame class and the corresponding <code>Curve</code> method. There are two problems: </p>
  
  <p>1) I do not know how to access the index once the DataFrame is inside the DFrame. </p>
  
  <p>2) I get a TypeError when including the index explicitly as a column and calling <code>Curve</code>. </p>
  
  <p>See here for the full notebook
  <a href="http://nbviewer.ipython.org/urls/gist.githubusercontent.com/bjonen/492fea9559fd73edf579/raw/ac01b49edde36bf621d90cc390baa790621290bd/holoviews_plt_tseries.ipynb" rel="nofollow">http://nbviewer.ipython.org/urls/gist.githubusercontent.com/bjonen/492fea9559fd73edf579/raw/ac01b49edde36bf621d90cc390baa790621290bd/holoviews_plt_tseries.ipynb</a></p>
  
  <p>The documentation has an example with Timestamps but in this example a <code>HoloMap</code> is generated and not a <code>Curve</code>. </p>
  
  <p>After doing some more investigation, it seems that <code>Curve</code> expects some kind of numerical data as <code>kdim</code>. The <code>TypeError</code> occurs when internally np.vstack is called on numpy arrays of float and object type. </p>
  
  <p>Any hints are well appreciated! </p>