he alpha on the hex string</p></td>
    </tr>
    <tr>
      <th>stroke_to</th>
      <td><p>column of <code>data</code> or hex colour to use as the ending stroke colour.
If using a hex colour, use either a single value, or a column of hex colours  on <code>data</code></p></td>
    </tr>
    <tr>
      <th>stroke_to_opacity</th>
      <td><p>Either a string specifying the
column of <code>data</code> containing the stroke opacity of each shape, or a value
between 1 and 255 to be applied to all the shapes. If