title: different color for dots in ggplot2
body: <p>I want to draw a scatter plot with R. I use ggplot2 to draw the picture:</p>
  
  <pre><code>data&lt;-data.frame(x=runif(50),y=runif(50))
  ggplot(data, aes(x,y))+geom_point()
  </code></pre>
  
  <p>but I want the dots to have different colors according to the "x" value, the dots belongs to the following "x" ranges must have different colors. [0,0.2), [0.2,0.4), [0.4,0.6), [0.6,0.8),[0.8,1].</p>