rvival/man/Surv.html'>Surv()</a></code> in package <code>survival</code>
          produces such a matrix</p></td>
    </tr>
    <tr>
      <th>x</th>
      <td><p>input matrix. Like for the glmnet function:
of dimension nobs x nvars; each row is an
observation vector. Can be in sparse matrix format (inherit
from class <code>"sparseMatrix"</code> as in package <code>Matrix</code>; not yet
available for <code>family="cox"</code>)</p></td>
    </tr>
    <tr>
      <th>size</th>
      <td><p>proportion of samp