title: how to overlay a line plot with a density plot? (R, ggplot2)
body: <p>Hi how do I overlap the following curves in one graph? Any help's appreciated. Thank you!</p>
  
  <pre><code>library(ggplot2)
  
  x = -10:10
  y = dnorm(x, mean=0, sd=3)
  df.norm = data.frame('x'=x, 'y'=y)
  
  ggplot(data=df.norm, aes(x=x, y=y)) +
          geom_line() +
          geom_point()
  
  random = data.frame('x'=rnorm(1000, mean = 0, sd = 3))
  
  ggplot(random, aes(x=x)) + 
          geom_density(size=1)
  </code></pre>
  
  <p>I tried the following and it didn't work</p>
  
  <pre><code>ggplot(data=df.norm, aes(x=x, y=y)) +
          geom_line() +
          geom_point() +
          geom_density(random, aes(x=x), size=1)
  </code></pre>