title: Overlaid histograms in R (ggplot2 preferred)
body: <p>I am trying to create a layered histogram like this with ggplot2:
  <img src="https://i.stack.imgur.com/t1HV5.png" alt="Style plot that I&#39;d like to create"></p>
  
  <p>Here are some data and code that I thought would work:</p>
  
  <pre><code>my.data &lt;- data.frame(treat = rep(c(0, 1), 100), prop_score = runif(2 * 100))
  my.data &lt;- transform(my.data, treat = ifelse(treat == 1, "treatment", "control"))
  my.data &lt;- transform(my.data, treat = as.factor(treat))
  my.fig &lt;- ggplot() + geom_histogram(data = my.data, binwidth = 0.05, alpha = 0.01, aes(x = prop_score, linetype = treat, position = identity)) 
  </code></pre>
  
  <p>But my code produces this:
  <img src="https://i.stack.imgur.com/WuuWz.png" alt="enter image description here"></p>
  
  <p>Thanks! I would prefer <code>ggplot2</code> (while I'm learning, I figured I just learn the common, extensible plotting language), but I'm open to anything/everything.</p>