ass="name" /><col class="desc" /></colgroup>
    <tr>
      <th>x</th>
      <td><p>an n x p matrix of covariates for the zero part data, where each row is an observation
and each column is a predictor. MUST be ordered such that the first n_s rows align with the
observations in x_s and s</p></td>
    </tr>
    <tr>
      <th>y</th>
      <td><p>a length n vector of responses taking positive values</p></td>
    </tr>
    <tr>
      <th>trt</th>
      <td><p>a length n vector of treatment variables with 1 ind