labelled, logical, numeric</td>
</tr>
</tbody>
</table>
<p>And then we make <code>refCat()</code> a proper summary function by using the <code>summaryFunction()</code> function to change its class:</p>
<pre class="r"><code>refCat &lt;- summaryFunction(refCat,
  description = &quot;Identify reference level&quot;,
  classes = c(&quot;factor&quot;)
  )</code></pre>
<p>and we see that <code>refCat</code> is now added to the output of <code>allSummaryFunctions()</code>:</p>
<pre class="r"><code>allSummaryFunctio