title: Using annotate to add different annotations to different facets
body: <p>I'm trying to add panel labels to different facets in a plot.  I want them to be 1:7, but, the following code</p>
  
  <pre><code>d &lt;- ggplot(diamonds, aes(carat, price, fill = ..density..)) +
       xlim(0, 2) + stat_binhex(na.rm = TRUE) + opts(aspect.ratio = 1)
  
  d1&lt;-d + facet_wrap(~ color)
  
  d1+annotate("text", x=0.25, y=1.5e+04, label=1:7)
  </code></pre>
  
  <p>yields</p>
  
  <pre><code>Error: When _setting_ aesthetics, they may only take one value. Problems: label
  </code></pre>
  
  <p>Now, I can supply a single value and get that replicated across all facets.  But how can I have different labels in different facets using annotate()?</p>