title: how to make the value on Y axis start from zero in R, ggplot2
body: <p>currently, I'm using ggplot2 to make density plot.</p>
  
  <pre><code>ggplot(data=resultFile,aes(x=V19, colour=V1) ) +
  geom_line(stat="density") +
  xlab("score") +
  ylab("density") +
  ggtitle(paste(data_name,protocol,level,sep=" ")) +
  theme(legend.title=element_blank(), legend.position=c(0.92,0.9)) +
  scale_color_manual(values=c("blue","red"),
                     labels=c("A", "B"))
  </code></pre>
  
  <p>using this code, I can get the plot below.
  <a href="https://i.stack.imgur.com/MzRmC.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/MzRmC.png" alt="enter image description here"></a></p>
  
  <p>However, I can get different plot if I used plot(density()...) function in R.
  <a href="https://i.stack.imgur.com/f3Jap.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/f3Jap.png" alt="enter image description here"></a></p>
  
  <p>Y value starts from 0.  </p>
  
  <p>How can I make the ggplot's plot as like plot(density()...) in R?</p>