lass='st'>"B"</span><span class='op'>)</span>,
  b <span class='op'>=</span> <span class='fu'><a href='https://rdrr.io/r/base/c.html'>c</a></span><span class='op'>(</span><span class='st'>"C"</span>, <span class='st'>"D"</span><span class='op'>)</span>,
  untouched <span class='op'>=</span> <span class='fu'><a href='https://rdrr.io/r/base/c.html'>c</a></span><span class='op'>(</span><span class='fl'>1</span>, <span class='fl'>2</span><span class='op'>)</span>
<span class='op'>)</span>
<span class='va'>df</s