by <span class="op">=</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="st">"countries"</span><span class="op">=</span><span class="st">"Nation|COUNTRY"</span>, <span class="st">"sector"</span><span class="op">=</span><span class="st">"[Ii]ndustry"</span><span class="op">)</span><span class="op">)</span></span></span>
<span class="r-out co"><span class="r-pr">#&gt;</span> Identifying columns to merge</span>
<span class="r-