title: Add standard error as shaded area instead of errorbars in geom_boxplot
body: <p>I have my <code>boxplot</code> and I added the mean with <code>stat_summary</code> as a line over the box plot. I want to add the <em>standard error</em>, but I don't want <em>errorbar</em>.</p>
  
  <p>Basically, I want to add the <em>standard error</em> as <em>shaded area</em>, as you can do using <code>geom_ribbon</code>.</p>
  
  <p>I used the <code>PlantGrowth</code> dataset to show you briefly what I've tried.</p>
  
  <pre class="lang-r prettyprint-override"><code>library(ggplot2) 
  
  ggplot(PlantGrowth, aes(group, weight))+ 
  stat_boxplot( geom='errorbar', linetype=1, width=0.5)+ 
  geom_boxplot(fill="yellow4",colour="black",outlier.shape=NA) + 
  stat_summary(fun.y=mean, colour="black", geom="line", shape=18, size=1,aes(group=1))+ 
  stat_summary(fun.data = mean_se, geom = "errorbar")
  </code></pre>
  
  <p>I did it using <code>geom_errorbar</code> in <code>stat_summary</code>, and tried to substitute <code>geom_errorbar</code> with <code>geom_ribbon</code>, as I saw in some other examples around the web, but it doesn't work.</p>
  
  <p>Something like this one, but with the error as shaded area instead of error bars (which make it a bit confusing to see)</p>
  
  <p><a href="https://i.stack.imgur.com/Nb2FX.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/Nb2FX.png" alt="enter image description here"></a></p>