ents are named, those names will be used in the data
frame returned (see details).  Such names may not be among the names of the named
arguments of <code>df_stats</code>().</p>
<p>If a function is specified using <code>::</code>, be sure to include the trailing
parens, even if there are no additional arguments required.</p></dd>


<dt>drop</dt>
<dd><p>A logical indicating whether combinations of the grouping
variables that do not occur in <code>data</code> should be dropped from the
result.</p></dd>


<dt>f