de> can be provided, giving instructions
for rows or columns to aggregate and the names of the results.
<code>aggregation_map</code> should be a list of named strings. The
entries in the list give names of rows and columns to be aggregated. The
names of the list entries provide the names of the resulting
aggregates.</p>
<div class="sourceCode" id="cb2"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="va">m</span></span>
<span><span class="co">#&gt;       John Paul George Ring