th>variables</th>
      <td><p>A character vectors with the names of the variables to be
plotted (optional).</p></td>
    </tr>
    <tr>
      <th>ci</th>
      <td><p>Numeric. What confidence interval should the errorbars span?
Defaults to a 95% confidence interval. Set to NULL to remove errorbars.</p></td>
    </tr>
    <tr>
      <th>sd</th>
      <td><p>Logical. Whether to display a box encompassing +/- 1SD Defaults to
TRUE.</p></td>
    </tr>
    <tr>
      <th>add_line</th>
      <td><p>Logical. Wheth