title: R ggplot2 - geom_segment + facet_grid does not line up correctly
body: <p>I can't seem to get the geom_segement to match up when add facet_grid</p>
  
  <pre><code>library(tidyverse)
  library(plotly)
  
  #create data frame in long format
  df &lt;- mtcars %&gt;% rownames_to_column(var = "car") %&gt;% 
    select(car, mpg, disp, cyl) %&gt;% 
    mutate(car = as.factor(car)) %&gt;% 
    pivot_longer(cols = c(mpg, disp)) %&gt;% 
    rowwise() %&gt;% 
    mutate(target = runif(1, value*.8, value*1.2))
  
  #create ggplot 
     ggplot(df) +
      scale_x_discrete() +
       geom_col(aes(x = car, y = value)) +
       geom_segment(
         aes(
           x = as.numeric(car)-.25,
           xend = as.numeric(car)+.25,
           y = target,
           yend = target
         ),
         linetype = 'dotted',
         color = 'black'
       ) +
        facet_grid(
          rows = vars(cyl),
          cols = vars(name),
          scales = "free",
          space = "free_y"
        ) +
        coord_flip()
  </code></pre>
  
  <p>As you can see below the 'reference lines' I'm creating with geom_segement aren't correct, they should be over the geom_col()</p>
  
  <p><a href="https://i.stack.imgur.com/TFR9E.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/TFR9E.jpg" alt="enter image description here"></a></p>