> <span class="va">arr_delay</span> <span class="op">-</span> <span class="va">dep_delay</span></span>
<span><span class="op">)</span></span></code></pre></div>
</div>
<div class="section level3">
<h3 id="summarise-values-with-summarise_dt">Summarise values with <code>summarise_dt()</code><a class="anchor" aria-label="anchor" href="#summarise-values-with-summarise_dt"></a>
</h3>
<div class="sourceCode" id="cb12"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="fu"><a href="..