name" /><col class="desc" /></colgroup>
    <tr>
      <th>...</th>
      <td><p>variables (vectors) that, together, make up the ID variables in the data and uniquely identifies the individual. Note that <code>id_variable()</code> will not check whether you've selected an appropriate set of variables; try running <code><a href='as_pibble.html'>as_pibble()</a></code> after getting your ID and time variables.</p></td>
    </tr>
    <tr>
      <th>.method</th>
      <td><p>Can be <code>'number'</code>, <code>'