iv class="sourceCode" id="cb21"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="co"># data.table</span></span>
<span><span class="va">flights</span><span class="op">[</span>, <span class="fu"><a href="https://rdrr.io/r/base/sum.html" class="external-link">sum</a></span><span class="op">(</span> <span class="op">(</span><span class="va">arr_delay</span> <span class="op">+</span> <span class="va">dep_delay</span><span class="op">)</span> <span class="op">&lt;</span> <span clas