title: Calculate mean after new recording
body: <p>I´m reading some excel files where I want to calculate the mean of the column 'Duration' but I want to see the change in mean after recording 1, 2, 3 and so on. So for the below table it would be:</p>
  <p><code>Mean1 = (3+3+3/3)</code></p>
  <p><code>Mean2 = (3+3+3+4+6/5)</code></p>
  <p><code>Mean3 = (3+3+3+4+6+4+3+1+4/9)</code></p>
  <p>Each file can have different number of recordings (but always starting from 1) and different number of durations for each recording.</p>
  <p>Is is possible in Python to make a script that does this automatically?</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>Recording</th>
  <th>Duration</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>1</td>
  <td>3</td>
  </tr>
  <tr>
  <td>1</td>
  <td>3</td>
  </tr>
  <tr>
  <td>1</td>
  <td>3</td>
  </tr>
  <tr>
  <td>2</td>
  <td>4</td>
  </tr>
  <tr>
  <td>2</td>
  <td>6</td>
  </tr>
  <tr>
  <td>3</td>
  <td>4</td>
  </tr>
  <tr>
  <td>3</td>
  <td>3</td>
  </tr>
  <tr>
  <td>3</td>
  <td>1</td>
  </tr>
  <tr>
  <td>3</td>
  <td>4</td>
  </tr>
  </tbody>
  </table>
  </div>