title: Getting an error that ggplot2_3.2.0 can't draw more than one boxplot per group
body: <p>I have <code>xy</code> data that I'd like to plot using <code>R</code>'s <code>ggplot</code>:</p>
  
  <pre><code>library(dplyr)
  library(ggplot2)
  set.seed(1)
  
  df &lt;- data.frame(group = unlist(lapply(LETTERS[1:5],function(l) rep(l,5))),
                   x = rep(1:5,5),
                   y = rnorm(25,2,1),
                   y.se = runif(25,0,0.1)) %&gt;%
    dplyr::mutate(y.min = y-3*y.se,
                  y.low = y-y.se,
                  y.high = y+y.se,
                  y.max = y+3*y.se)
  </code></pre>
  
  <p>As you can see, while <code>df$x</code> is a point (<code>integer</code>), <code>df$y</code> has an associated error, which I would like to include using a box plot.</p>
  
  <p>So my purpose is to plot each row in <code>df</code> by its <code>x</code> coordinate, using <code>y.min</code>, <code>y.low</code>, <code>y</code>, <code>y.high</code>, and <code>y.max</code> to construct a <code>boxplot</code>, and <code>color</code> and <code>fill</code> it by <code>group</code>. That means, that I'd like to have each row in <code>df</code>, plotted as a <code>box</code> along a separate <code>x-axis</code> location and <code>faceted</code> by <code>df$group</code>, such that <code>df$group</code> <code>A</code>'s five replicates appear first, then to their right <code>df$group</code> <code>B</code>'s replicates, and so on.</p>
  
  <p>This code used to work for my purpose until I just installed the latest <code>ggplot2</code> package (<code>ggplot2_3.2.0</code>):</p>
  
  <pre><code>ggplot(df,aes(x=x,ymin=y.min,lower=y.low,middle=y,upper=y.high,ymax=y.max,col=group,fill=group))+
  geom_boxplot(position=position_dodge(width=0),alpha=0.5,stat="identity")+
  facet_grid(~group,scales="free_x")+scale_x_continuous(breaks = integerBreaks())
  </code></pre>
  
  <p>Now I'm getting this error:</p>
  
  <pre><code>Error: Can't draw more than one boxplot per group. Did you forget aes(group = ...)?
  </code></pre>
  
  <p>Any idea?</p>