z</th>
      <td><p>a matrix containing the values to compute contour lines for</p></td>
    </tr>
    <tr>
      <th>x, y</th>
      <td><p>locations of grid lines at which the values in <code>image</code> are measured (see <code><a href='https://rdrr.io/r/grDevices/contourLines.html'>contourLines</a></code>)</p></td>
    </tr>
    <tr>
      <th>nlevels, levels</th>
      <td><p>parameters sent to <code><a href='https://rdrr.io/r/grDevices/contourLines.html'>contourLines</a></code>)</p></td>
    </tr>
   