Use Panda's diff() against first column/row of data.frame
<p>assume you have a dataframe where the first column is a date and the consecutive columns are values adjusted over time. F.x. the prognosis of wind for a specific date changes over time as new information is available.</p>

<p>My task is to compute the difference in regards to the <strong>first</strong> column. 
So the principle is similar to pandas.DataFrame.diff but the reference value is not the preceding column but always the first.</p>

<p>So assuming your dataframe looks like this</p>

<pre><code>Date    Forecast1    Forecast2    Forecast3        
1/1/15    5             3              7
</code></pre>

<p>I want the result to look like this:</p>

<pre><code>Date    Forecast1    Forecast2    Forecast3        
1/1/15    NaN             -2          2
</code></pre>

<p>I hope my explanation was clear.</p>

<p>Thank you for your efforts.</p>