span class="st">"Paul"</span>, <span class="st">"George"</span><span class="op">)</span><span class="op">)</span><span class="op">)</span></span>
<span><span class="co">#&gt;       guitarists Ringo</span></span>
<span><span class="co">#&gt; birds         54    24</span></span></code></pre></div>
<p>The margin over which the aggregation is to be performed is given by
the <code>margin</code> argument (<code>1</code> for rows,
<code>2</code> for columns).</p>
<div class="sourceCode" id="cb3"><pre class="downli