/head.html" class="external-link">head</a></span><span class="op">(</span><span class="fu"><a href="reference/drop_na_at.html">drop_na_at</a></span><span class="op">(</span><span class="va">airquality</span>,pattern_type <span class="op">=</span> <span class="st">"starts_with"</span>,<span class="st">"O"</span><span class="op">)</span><span class="op">)</span>
<span class="co">#&gt;   Ozone</span>
<span class="co">#&gt; 1    41</span>
<span class="co">#&gt; 2    36</span>
<span class="co">#&gt; 3    12</spa