a href="crossing.html">crossing()</a></code> </p>
        </td>
        <td><p>Create a data.table from all unique combinations of inputs</p></td>
      </tr><tr><td>
          <p><code><a href="drop_na.html">drop_na()</a></code> </p>
        </td>
        <td><p>Drop rows containing missing values</p></td>
      </tr><tr><td>
          <p><code><a href="expand.html">expand()</a></code> <code><a href="expand.html">nesting()</a></code> </p>
        </td>
        <td><p>Expand a data.table to use all combinat