title: stat_summary_bin at x-axis ticks
body: <p>
  How do I make ggplot's <code>stat_summary_bin</code> do the summaries at specified x-axis values? For example, in the plot below I'd like the summaries at x=-1, 0, 1, 2, etc. Now it's at -1.5, -0.5, 0.5, and 1.5.</p>
  
  <pre><code>df = data.frame(x=rnorm(1000), y=rnorm(1000))
  ggplot(df, aes(x=x, y=y)) +
  stat_summary_bin(binwidth=1)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/PzLAl.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/PzLAl.png" alt="enter image description here"></a></p>