ould unused factor levels be omitted from the scale?
The default, <code>TRUE</code>, uses the levels that appear in the data;
<code>FALSE</code> uses all the levels in the factor.</p></dd>

    <dt><code>guide</code></dt>
<dd><p>A function used to create a guide or its name. See
<code><a href="https://ggplot2.tidyverse.org/reference/guides.html" class="external-link">guides()</a></code> for more information.</p></dd>

    <dt><code>position</code></dt>
<dd><p>For position scales, The position of th