 the legend</p></li>
<li><p>digits - number to round the legend values to</p></li>
</ul>

<p>If the layer allows different fill and stroke colours, you can use different options for each. See examples in <a href='add_arc.html'>add_arc</a>.</p>
<p>The <code>legend_format</code> can be used to control the format of the values in the legend.
This should be a named list, where the names are one of</p><ul>
<li><p>fill_colour</p></li>
<li><p>stroke_colour</p></li>
</ul>

<p>depending on which type of colouring th