<span class="op">+</span><span class="fu"><a href="https://ggplot2.tidyverse.org/reference/geom_ribbon.html" class="external-link">geom_area</a></span><span class="op">(</span>fill<span class="op">=</span><span class="st">"grey"</span>, alpha<span class="op">=</span><span class="fl">.5</span><span class="op">)</span><span class="op">+</span><span class="va">apatheme</span></span></code></pre></div>
<p><img src="reference/figures/irt.png" title="Publication quality plots for Item Response Theory Based Analys