title: How to filter a specific column character in R after importing data with fread function
body: <p>I have imported in r a .tsv file with fread function from data.table package</p>
  <pre><code>dt &lt;- fread( &quot;full_data.tsv&quot;, nrows = 1000000)
  </code></pre>
  <p>the dataset have 37 columns, something like this:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;">ID</th>
  <th style="text-align: center;">DATA</th>
  <th style="text-align: right;">lan</th>
  <th style="text-align: right;">geo_coord</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">10002</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[10.2,32.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10003</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[12.2,42.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10004</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[14.4,22.6]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10005</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[32.6,23.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10004</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[16.2,21.2]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10006</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[16.7,20.2]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10007</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">10008</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;"></td>
  </tr>
  <tr>
  <td style="text-align: left;">10009</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;"></td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I would filter only geo-coord column (character) in order to remove empty cells obtaining a result like this:</p>
  <div class="s-table-container">
  <table class="s-table">
  <thead>
  <tr>
  <th style="text-align: left;">ID</th>
  <th style="text-align: center;">DATA</th>
  <th style="text-align: right;">lan</th>
  <th style="text-align: right;">geo_coord</th>
  </tr>
  </thead>
  <tbody>
  <tr>
  <td style="text-align: left;">10002</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[10.2,32.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10003</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[12.2,42.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10004</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[14.4,22.6]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10005</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[32.6,23.5]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10004</td>
  <td style="text-align: center;">2020-02-01</td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[16.2,21.2]</td>
  </tr>
  <tr>
  <td style="text-align: left;">10006</td>
  <td style="text-align: center;"></td>
  <td style="text-align: right;">eng</td>
  <td style="text-align: right;">[16.7,20.2]</td>
  </tr>
  </tbody>
  </table>
  </div>
  <p>I tried with filter from dplyr without result.</p>