title: ggplot2: Making changes to symbols in the legend
body: <p>I'm having a problem making the symbols in the legend of my plot match those in the plot itself.  </p>
  
  <p>Suppose the data has four columns like this </p>
  
  <pre><code>data = data.frame(x = sample(1:10, 10, replace=TRUE), y = sample(1:10, 10, replace=TRUE), 
             Rank = sample(1:10, 10, replace = TRUE), Quantified = factor(sample(1:2, 10, replace = TRUE))
  )
  </code></pre>
  
  <p>I would like points to be different sizes (distinguished by 'Rank') and represented by different symbols (crosses and open circles, distinguished by 'Quantified').  </p>
  
  <p>My code is </p>
  
  <pre><code>ggplot(data, aes(x = x, y = y)) +
            geom_point(aes(size = Rank, shape = Quantified)) +
            scale_shape_manual("Quantified", labels = c("Yes", "No"), values = c(1, 4)
   )
  </code></pre>
  
  <p>The symbols in the plot are as I want them.  </p>
  
  <p>My problem is that I would like the circles in the top legend to be <strong>unfilled</strong> as they are in the plot.  </p>
  
  <p>I've tried a variety of commands in different parts of the code (e.g., fill = "white") but nothing seems to work quite right.</p>
  
  <p>Any suggestions?  </p>