title: Boxed geom_text with ggplot2
body: <p>I am developing a graphic with ggplot2 wherein I need to superimpose text over other graphical elements. Depending on the color of the elements underlying the text, it can be difficult to read the text. Is there a way to draw geom_text in a bounding box with a semi-transparent background?</p>
  
  <p>I can do this with plotrix:</p>
  
  <pre><code>library(plotrix)
  Labels &lt;- c("Alabama", "Alaska", "Arizona", "Arkansas")
  SampleFrame &lt;- data.frame(X = 1:10, Y = 1:10)
  TextFrame &lt;- data.frame(X = 4:7, Y = 4:7, LAB = Labels)
  ### plotrix ###
  plot(SampleFrame, pch = 20, cex = 20)
  boxed.labels(TextFrame$X, TextFrame$Y, TextFrame$LAB,
   bg = "#ffffff99", border = FALSE,
   xpad = 3/2, ypad = 3/2)
  </code></pre>
  
  <p>But I do not know of a way to achieve similar results with ggplot2:</p>
  
  <pre><code>### ggplot2 ###
  library(ggplot2)
  Plot &lt;- ggplot(data = SampleFrame,
   aes(x = X, y = Y)) + geom_point(size = 20)
  Plot &lt;- Plot + geom_text(data = TextFrame,
   aes(x = X, y = Y, label = LAB))
  print(Plot)
  </code></pre>
  
  <p>As you can see, the black text labels are impossible to perceive where they overlap the black geom_points in the background.</p>