ourceCode"><pre class="sourceCode r"><code><span class="r-in"><span class="va">conf</span> <span class="op">&lt;-</span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span></span>
<span class="r-in"> columns <span class="op">=</span> <span class="fu"><a href="https://rdrr.io/r/base/list.html" class="external-link">list</a></span><span class="op">(</span></span>
<span class="r-in">   first_column <span class="op">=</span> <span class="fu"