<h3 id="refer-to-columns-by-names">Refer to columns by names<a class="anchor" aria-label="anchor" href="#refer-to-columns-by-names"></a>
</h3>
<div class="sourceCode" id="cb22"><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/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"arr_delay"</span>, <span 