title: How can I put a transformed scale on the right side of a ggplot2?
body: <p>I'm creating a graph showing the change in lake levels over time. I've attached a simple example below. I would like to add a scale (tick marks and annotation) on the right side of the plot that shows the elevation in feet. I know ggplot2 won't allow two different scales (see <a href="https://stackoverflow.com/questions/3099219/how-to-use-ggplot2-make-plot-with-2-y-axes-one-y-axis-on-the-left-and-another">Plot with 2 y axes, one y axis on the left, and another y axis on the right</a>), but because this is a transformation of the same scale, is there a way to do this? I'd prefer to keep using ggplot2 and not to have to revert to the plot() function.</p>
  
  <pre><code>library(ggplot2)
  LakeLevels&lt;-data.frame(Day=c(1:365),Elevation=sin(seq(0,2*pi,2*pi/364))*10+100)
  p &lt;- ggplot(data=LakeLevels) + geom_line(aes(x=Day,y=Elevation)) + 
    scale_y_continuous(name="Elevation (m)",limits=c(75,125)) 
  p
  </code></pre>