args</dt>
<dd><p>Arguments passed to the functions in <code>...</code>.</p></dd>


<dt>sep</dt>
<dd><p>A character string to separate components of names.  Set to <code>""</code> if
you don't want separation.</p></dd>


<dt>format</dt>
<dd><p>One of <code>"long"</code> or <code>"wide"</code> indicating the desired shape of the
returned data frame.</p></dd>


<dt>groups</dt>
<dd><p>An expression or formula to be evaluated in <code>data</code> and defining (additional) groups.
This isn't necessary, since thes