<code>NULL</code> which will shade the bars by the <code>split_by</code>
variable.</p></td>
    </tr>
    <tr>
      <th>count</th>
      <td><p><strong>for pre-computed data</strong> the name of the column in the data
frame for the values of the bars. If this represents proportions, the
values should be within [0, 1].</p></td>
    </tr>
    <tr>
      <th>proportional</th>
      <td><p>If <code>TRUE</code>, bars will represent proportions of cases out
of the entire population. Otherwise (<code>FALSE</code>