title: Symmetric y-axis limits for barchart in ggplot2
body: <p>I would like to make the y-axis of a bar chart symmetric, so that it's easier to see if positive or negative changes are bigger. Since otherwise this is a bit distorted. I do have working code although it's a bit clumsy and I thought it would be great if I could directly do this in the first <code>ggplot()</code> call. So as to say that <code>ylim</code> directly is symmetrical.</p>
  
  <pre><code>set.seed(123)
  my.plot &lt;- ggplot( data = data.table(x = 1:10,
                            y = rnorm(10,0, 2)), aes(x=x, y=y)) +
          geom_bar(stat="identity")
  
  rangepull &lt;- layer_scales(my.plot)$y
  newrange &lt;- max(abs(rangepull$range$range))
  my.plot +
               ylim(newrange*-1, newrange)
  </code></pre>