title: label and add legends on density plot
body: <p>I am trying to draw two density graphs on the same plot. I tried the following code.</p>
  
  <pre><code>car     Bus
  48.1    17.8
  47.2    21.2
  69.9    27
  72.7    9.1
  73.8    23.9
  67.7    4.9
  61.1    12.3
  61.6    0.4
          4.7
          20.9
          5.5
          19.8
           5.9
          14.3
          16.3
  
  
   library(ggplot2)
  m &lt;-ggplot()+geom_density(aes(data$column1),color='red')+geom_density(aes(data$column2), color='blue') 
  </code></pre>
  
  <p>The code gives what I want. But I have to label x-axis and also need to add legends. How can I achieve this?</p>