select some items</span></span>
<span><span class="va">items</span> <span class="op">&lt;-</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="fu"><a href="https://rdrr.io/r/base/grep.html" class="external-link">grep</a></span><span class="op">(</span> <span class="st">"O"</span>, <span class="fu"><a href="https://rdrr.io/r/base/colnames.html" class="external-link">colnames</a></span><span class="op">(</span><span class="va