title: ggplot 'non-finite values' error
body: <p>I have an R dataframe (<code>df</code>) that looks like this:</p>
  
  <pre><code>blogger; word; n; total
  joe; dorothy; 17; 718
  paul; sheriff; 10; 354
  joe; gray; 9; 718
  joe; toto; 9; 718
  mick; robin; 9; 607
  paul; robin; 9; 354
  ...
  </code></pre>
  
  <p>I want to use <code>ggplot2</code> to plot <code>n</code> divided by <code>total</code> for each <code>blogger</code>.</p>
  
  <p>I have this code:</p>
  
  <pre><code>ggplot(df, aes(n/total, fill = blogger)) +
    geom_histogram(show.legend = FALSE) +
    xlim(NA, 0.0004) +
    facet_wrap(~blogger, ncol = 2, scales = "free_y")
  </code></pre>
  
  <p>But it yields this warning:</p>
  
  <pre><code>Warning message:
  “Removed 1474 rows containing non-finite values (stat_bin).”Warning message in rep(no, length.out = length(ans)):
  “'x' is NULL so the result will be NULL”
  </code></pre>