title: Normalize each column of a pandas DataFrame
body: <p>Each column of the Dataframe needs their values to be normalized according the value of the first element in that column.</p>
  
  <pre><code>for timestamp, prices in data.iteritems():
      normalizedPrices = prices / prices[0]
      print normalizedPrices     # how do we update the DataFrame with this Series?
  </code></pre>
  
  <p>However how do we update the DataFrame once we have created the normalized column of data? I believe if we do <code>prices = normalizedPrices</code> we are merely acting on a copy/view of the DataFrame rather than the original DataFrame itself.</p>