class="sourceCode" id="cb3"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span class="co"># install devtools if required</span>
<span class="kw">if</span> <span class="op">(</span><span class="op">!</span><span class="kw"><a href="https://rdrr.io/r/base/library.html" class="external-link">require</a></span><span class="op">(</span><span class="st"><a href="https://devtools.r-lib.org/" class="external-link">"devtools"</a></span><span class="op">)</span><span class="op">)</span> <span class="