title: Change index col with pandas and read_excel
body: <p>I have a excel file with 6 columns and i want use the 3 column for my index </p>
  
  <p>when I print without changing the index the output like this </p>
  
  <p><code>df = pd.read_excel('sp500.xlsx')
   print(df.head())</code></p>
  
  <pre><code>    close            ctm                      Date    high     low    open  
  0  1831.9  1389135600000   Jan 8, 2014 12:00:00 AM  1834.7  1825.5  1830.5   
  1  1833.6  1389222000000   Jan 9, 2014 12:00:00 AM  1838.7  1824.3  1831.0   
  2  1836.5  1389308400000  Jan 10, 2014 12:00:00 AM  1842.1  1826.3  1832.8   
  3  1815.0  1389567600000  Jan 13, 2014 12:00:00 AM  1838.0  1809.5  1837.5   
  4  1832.8  1389654000000  Jan 14, 2014 12:00:00 AM  1834.0  1812.5  1815.0 
  </code></pre>
  
  <p>but when i change the index like this </p>
  
  <pre><code>df = pd.read_excel('sp500.xlsx', parse_dates=True, index_col=3)
  print(df.head())
  </code></pre>
  
  <p>i have this</p>
  
  <pre><code>             close   ctm           Date    high     low    open 
  2014-01-08      0  1831.9  1389135600000  1834.7  1825.5  1830.5    
  2014-01-09      1  1833.6  1389222000000  1838.7  1824.3  1831.0    
  2014-01-10      2  1836.5  1389308400000  1842.1  1826.3  1832.8    
  2014-01-13      3  1815.0  1389567600000  1838.0  1809.5  1837.5    
  2014-01-14      4  1832.8  1389654000000  1834.0  1812.5  1815.0    
  </code></pre>
  
  <p>each column are moved from one and my close column is my old index </p>