an><span class="ot">NULL</span>]</span>
<span id="cb15-3"><a href="#cb15-3" aria-hidden="true"></a><span class="kw">head</span>(flights)</span>
<span id="cb15-4"><a href="#cb15-4" aria-hidden="true"></a><span class="co">#    year month day dep_delay arr_delay carrier origin dest air_time distance hour</span></span>
<span id="cb15-5"><a href="#cb15-5" aria-hidden="true"></a><span class="co"># 1: 2014     1   1        14        13      AA    JFK  LAX      359     2475    9</span></span>
<span id="cb15-6"><a h