 that indicates the unique objects (towns in this case). We can see how many towns we have in the resulting dataset:</p>
<div class="sourceCode" id="cb8"><pre class="sourceCode R"><code class="sourceCode r"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true"></a><span class="op">&gt;</span><span class="st"> </span><span class="kw">length</span>(<span class="kw">unique</span>(res<span class="op">$</span>group))</span>
<span id="cb8-2"><a href="#cb8-2" aria-hidden="true"></a>[<span class="dv">1</span>] <span