es, we’ll use the <code>fev</code> dataset. This
dataset is included in the <code>rigr</code> package; see its
documentation by running <code><a href="../reference/fev.html">?fev</a></code>.</p>
<div class="sourceCode" id="cb1"><pre class="downlit sourceCode r">
<code class="sourceCode R"><span><span class="co">## Preparing our R session</span></span>
<span><span class="kw"><a href="https://rdrr.io/r/base/library.html" class="external-link">library</a></span><span class="op">(</span><span class="va"><a hr