 class="r-in"><span><span class="co"># create new column representing the zone id that each planning unit</span></span></span>
<span class="r-in"><span><span class="co"># was allocated to in the solution</span></span></span>
<span class="r-in"><span><span class="va">s3</span><span class="op">$</span><span class="va">solution</span> <span class="op">&lt;-</span> <span class="fu"><a href="category_vector.html">category_vector</a></span><span class="op">(</span></span></span>
<span class="r-in"><span>  <span c