d="cb26"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span class="co"># recode at columns that start with O or S(case sensitive)</span>
<span class="fu"><a href="https://rdrr.io/r/utils/head.html" class="external-link">head</a></span><span class="op">(</span><span class="fu"><a href="reference/recode_as_na.html">recode_as_na</a></span><span class="op">(</span><span class="va">airquality</span>,value<span class="op">=</span><span class="fu"><a href="https://rdrr.io/r/base/c.html" class="ext