title: Most frequent factor in a group by operation, in R
body: <p>I have a dataframe like this:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID_CLI</th>
  <th>CHURN</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>12</td>
  <td>0</td>
  </tr>
  <tr>
  <td>12</td>
  <td>0</td>
  </tr>
  <tr>
  <td>25</td>
  <td>1</td>
  </tr>
  <tr>
  <td>25</td>
  <td>1</td>
  </tr>
  <tr>
  <td>25</td>
  <td>1</td>
  </tr>
  <tr>
  <td>27</td>
  <td>0</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I want to group by on ID_CLI and have an output like this:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th>ID_CLI</th>
  <th>CHURN</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td>12</td>
  <td>0</td>
  </tr>
  <tr>
  <td>25</td>
  <td>1</td>
  </tr>
  <tr>
  <td>27</td>
  <td>0</td>
  </tr>
  </tbody>
  </table>
  </div>