an><span class="va">res</span><span class="op">$</span><span class="va">m</span><span class="op">[[</span><span class="fl">2</span><span class="op">]</span><span class="op">]</span></span>
<span><span class="co">#&gt;    c1 c2 c3</span></span>
<span><span class="co">#&gt; r1 11 12 13</span></span>
<span><span class="co">#&gt; r2 21 22 23</span></span></code></pre></div>
</div>
<div class="section level2">
<h2 id="working-with-aggregation-maps">Working with aggregation maps<a class="anchor" aria-label="ancho