vtools</code> package. In R, type:</p>
<pre><code><span><span class="kw">if</span> <span class="op">(</span><span class="op">!</span><span class="fu"><a href="https://rdrr.io/r/base/ns-load.html" class="external-link">requireNamespace</a></span><span class="op">(</span><span class="st">"devtools"</span>, quietly <span class="op">=</span> <span class="cn">TRUE</span><span class="op">)</span><span class="op">)</span> </span>
<span>    <span class="fu"><a href="https://rdrr.io/r/utils/install.packages.html" cl