title: shading the area around the quantile regression median line
body: <p>I have used the stat_quantile function in ggplot2 to generate three quantile regression lines corresponding to the 5th, 50th and 95th percentiles. I would like to shade the area between the 5th and 95th percentiles, (maintaining the 50th percentile line). I know I can use geom_ribbon to set the upper (95th percentile) and lower (5th percentile) bounds, but how do I calculate these bounds using ggplot2 so that I can use them in the geom_ribbon function? Can it even be done? I'm very confused about this. Please help. here is part of the data</p>
  
  <pre><code>     snps&lt;-c(1.542685,1.576102,1.576102,1.576102,1.576102,1.623212,1.655293,1.649179,1.657021,1.626873,1.749787,1.7524,1.746435,1.780996,1.790124)   
       distance&lt;-c(0.1,0.1,0.1,0.1,0.1,0.2,0.2,0.2,0.2,0.2,0.7,0.7,0.7,0.7,0.7)
       df&lt;-data.frame(snps,distance)
      ggplot(df, aes(distance,snps)) + geom_point(alpha=0)+
      stat_quantile(mapping = NULL, data = NULL, geom = "quantile", position ="identity",quantiles = c(0.05, 0.5, 0.95), lambda = 100,method="rqss",formula = NULL, na.rm = FALSE,size=1.5) +theme(legend.position="none")
  </code></pre>
  
  <p>the data produces three lines corresponding to the quantiles. What I would like to do is shade the area around the median, between the two outer bounds.
  Also, is there a way to omit these two outer lines so that they form something like an invincible boundary?</p>