></span>
<span></span>
<span><span class="co"># N by sex</span></span>
<span><span class="va">student</span><span class="op">[</span><span class="fu"><a href="https://rdrr.io/r/base/order.html" class="external-link">order</a></span><span class="op">(</span><span class="va">sex</span><span class="op">)</span>, <span class="va">.N</span>, by <span class="op">=</span> <span class="st">"sex"</span><span class="op">]</span></span>
<span><span class="co">#&gt;        sex     N</span></span>
<span><span class="co"