ss="fu"><a href="https://rdrr.io/r/base/c.html" class="external-link">c</a></span><span class="op">(</span><span class="st">"a"</span>, <span class="st">"b"</span>, <span class="cn">NA</span>, <span class="st">"NA"</span><span class="op">)</span>,y <span class="op">=</span> <span class="fl">1</span><span class="op">:</span><span class="fl">4</span><span class="op">)</span></span></span>
<span class="r-in"><span><span class="va">df</span> <span class="op"><a href="https://magrittr.tidyverse.org/reference/pi