ata.frame or data.table</p></dd>


<dt id="arg--">...<a class="anchor" aria-label="anchor" href="#arg--"></a></dt>
<dd><p>Aggregations to perform</p></dd>


<dt id="arg--by">.by<a class="anchor" aria-label="anchor" href="#arg--by"></a></dt>
<dd><p>Columns to group by.</p><ul><li><p>A single column can be passed with <code>.by = d</code>.</p></li>
<li><p>Multiple columns can be passed with <code>.by = c(c, d)</code></p></li>
<li><p><code>tidyselect</code> can be used:</p><ul><li><p>Single predicate: <code>.b