title: How to fill part of density curve in ggridges together with facets
body: <p>I would like to color a specific area, where <code>col_bol = 1</code> in a <code>ggridges</code> density curve plot. I know its possible to do this using <code>stat_density_ridges()</code> providing quantiles. If I dont have the quantiles I calculate the percent. This works if it's only one plot without facets. </p>
  
  <p>How could I achieve it using the data below? </p>
  
  <pre><code>library(tidyverse)
  library(ggridges)
  
  plot_data &lt;- iris %&gt;% gather(key = 'key', value = 'value', -Species) %&gt;% mutate(col_bol =  case_when(
    Species == 'setosa' &amp; (value &lt; 1.5 | value &gt; 6) ~ 1,
    Species != 'setosa' &amp; (value &lt; 1.3 | value &gt; 6.2) ~ 1,
    TRUE ~ 0))
  
  
  ggplot(data = plot_data, mapping = aes(y = key, x = value)) +
    geom_density_ridges() +
    facet_wrap(~Species, scales = 'free_x') + 
    theme_ridges()
  </code></pre>