">
    <colgroup><col class="name" /><col class="desc" /></colgroup>
    <tr>
      <th>flow</th>
      <td><p>A data frame representing the flow between two points
or zones. The first two columns of this data frame should correspond
to the first column of the data in the zones. Thus in <code><a href='cents.html'>cents()</a></code>,
the first column is geo_code. This corresponds to the first two columns
of <code><a href='flow.html'>flow()</a></code>.</p></td>
    </tr>
    <tr>
      <th>zones</th>
      <t