title: ggplot2: Using formular in aes mapping
body: <p>With data iris I want to the color of point of setosa specie different to other species. The command works with != operator but =operator does not.</p>
  
  <p>I have two color with:</p>
  
  <pre><code>ggplot(iris)+ geom_point(aes(x=Sepal.Length,y=Petal.Length,**color=Species!="setosa"**))
  </code></pre>
  
  <p>I have only one color:</p>
  
  <pre><code>ggplot(iris)+ geom_point(aes(x=Sepal.Length,y=Petal.Length,**color=Species="setosa"**))
  </code></pre>