title: Cumsum with pandas on financial data
body: <p>I'm very new to python and I have managed to import data from an excel datasheet using the <code>pd.read_excel</code> function. The data is arranged in the following manner in a dataframe :</p>
  
  <p><a href="https://i.stack.imgur.com/Yw3jR.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Yw3jR.jpg" alt="enter image description here"></a></p>
  
  <p>I'm trying to do a cumsum() over this dataframe, however I get this error message : </p>
  
  <pre><code>TypeError: unsupported operand type(s) for +: 'Timestamp' and 'Timestamp'
  </code></pre>
  
  <p>How can I force only the cumsum() on the returns columns without removing my dates columns ?</p>
  
  <p>I added the data with the following function :<br>
  <code>oFX = pd.read_excel('C:\\Work\\Python Dev\\Athenes\\FX.xlsx', 0)</code></p>
  
  <p>The <code>data.info()</code> is the following :<br>
  <code>oFX.info()  &lt;class 'pandas.core.frame.DataFrame'&gt; 
  Int64Index: 4133 entries, 0 to 4132 
  Data columns (total 11 columns): 
  Dates    4133 non-null datetime64[ns] 
  AUD      4133 non-null float64 
  CAD      4133 non-null float64 
  CHF      4133 non-null float64 
  EUR      4133 non-null float64 
  GBP      4133 non-null float64 
  JPY      4133 non-null float64 
  KRW      4133 non-null float64 
  MEP      4133 non-null float64 
  NZD      4133 non-null float64 
  USD      4133 non-null float64 
  dtypes: datetime64[ns](1), float64(10) 
  memory usage: 387.5 KB</code></p>
  
  <p>Thanks in advance.</p>