col class="desc" /></colgroup>
    <tr>
      <th>data</th>
      <td><p>A data frame</p></td>
    </tr>
    <tr>
      <th>yname</th>
      <td><p>outcome variable</p></td>
    </tr>
    <tr>
      <th>gname</th>
      <td><p>variable for unit-specific date of treatment (missing = never-treated)</p></td>
    </tr>
    <tr>
      <th>tname</th>
      <td><p>variable for calendar period</p></td>
    </tr>
    <tr>
      <th>idname</th>
      <td><p>variable for unique unit id</p></td>
    </tr>
    <tr>
    