lot</span>(m) <span class="op">+</span>
<span class="st">  </span><span class="kw">facet_grid</span>(variable<span class="op">~</span>., <span class="dt">scales=</span><span class="st">&quot;free&quot;</span>)<span class="op">+</span>
<span class="st">  </span><span class="kw">geom_rect</span>(<span class="kw">aes</span>(<span class="dt">xmin=</span>xmin, <span class="dt">ymin=</span>ymin, <span class="dt">xmax=</span>xmax, <span class="dt">ymax=</span>ymax, 
                <span class="dt">fill=</span><sp