<a href="#fn6" class="footnote-ref" id="fnref6"><sup>6</sup></a> are treated as <strong>numerical, quantitative data</strong>.</p>
<p>The most important difference between the categorical types is their sorting: while <code>character</code> and also <code>logical</code> values are sorted alphabetically, <code>factor</code> variables have a specified order, defined by the so-called <em>levels</em>. Note that numbers can be treated as categorical as well and thus we can change their intrinsic order, too. We c