title: Python Pandas - weekly line graph from yearly data
body: <p>i have a yearly dataset with energy consumption readings in 30min intervals:</p>
  
  <pre><code>                      data
  2012-11-01 00:00:00  0.177
  2012-11-01 00:30:00  0.141
  2012-11-01 01:00:00  0.112
  2012-11-01 01:30:00  0.082
  2012-11-01 02:00:00  0.080
  ...
  </code></pre>
  
  <p>how do i plot a multiple line graph showing the data consumption for each week? i.e. eventually i will have a graph with 52 lines, where the x axis is the time in the week (days? half days? hours?) and the y axis is the consumption.</p>
  
  <p>thanks</p>