title: python pandas portfolio return
body: <p>I've got a dataframe with market data and one column dedicated to daily returns.
  I'm having a hard time creating a portfolio to start at $100,000.00 in value, and compute its cumulative return through the life of the data series.</p>
  
  <p>Ideally, I'd like to compute the 'portfolio' column using pandas but I'm having trouble doing so. See below target output. Thank you.</p>
  
  <pre><code>index    date      index  return  portfolio
  0        19900101  2000   Nan     100000.00
  1        19900102  2002   0.001   100100.00
  2        19900103  2020   0.00899 100999.90 
  3        19900104  2001  -0.00941 100049.49
  </code></pre>