title: GGplot second y axis without the transformation of y axis
body: <p>Does any one know how do you apply this</p>
  <pre><code>set.seed(101)
  x &lt;- 1:10
  y &lt;- rnorm(10)
  ## second data set on a very different scale
  z &lt;- runif(10, min=1000, max=10000) 
  par(mar = c(5, 4, 4, 4) + 0.3)  # Leave space for z axis
  plot(x, y) # first plot
  par(new = TRUE)
  plot(x, z, type = &quot;l&quot;, axes = FALSE, bty = &quot;n&quot;, xlab = &quot;&quot;, ylab = &quot;&quot;)
  axis(side=4, at = pretty(range(z)))
  mtext(&quot;z&quot;, side=4, line=3)
  </code></pre>
  <p>but using ggplot.</p>
  <p>In ggplot you can only create sec.axis() or dup.axis() using a transformation of y axis. What about a whole new independent y axis which will be applied only for z variable and the simple y axis to be applied for the y variable.</p>