ceCode r code-with-copy"><code class="sourceCode r"><span id="cb25-1"><a href="#cb25-1" aria-hidden="true" tabindex="-1"></a>polygon_layer <span class="ot">&lt;-</span> <span class="cf">function</span>(x, y, <span class="at">fill =</span> <span class="st">"white"</span>, <span class="at">alpha =</span> .<span class="dv">5</span>) {</span>
<span id="cb25-2"><a href="#cb25-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">geom_polygon</span>(<span class="fu">aes</span>(x, y), <span class="at">fill =<