title: plot (ggplot ?) smooth + color area between 2 curves
body: <p>I have a question for you please : </p>
  
  <p>My data : </p>
  
  <pre><code>    Nb_obs &lt;- as.vector(c( 2,  0,  6,  2,  7,  1,  8,  0,  2,  1,  1,  3, 11,  5,  9,  6,  4,  0,  7,  9))
      Nb_obst &lt;- as.vector(c(31, 35, 35, 35, 39, 39, 39, 39, 39, 41, 41, 42, 43, 43, 45, 45, 47, 48, 51, 51))
      inf20 &lt;- as.vector(c(2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 4, 3, 4, 4, 3, 5, 4))
      sup20 &lt;- as.vector(c(3, 4, 4, 4, 5, 4, 4, 5, 4, 4, 5, 5, 5, 6, 5, 6, 6, 5, 7, 6))
      inf40 &lt;- as.vector(c(1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 3, 3, 3, 4, 3))
      sup40 &lt;- as.vector(c(4, 5, 5, 5, 6, 5, 5, 6, 5, 5, 6, 6, 6, 7, 6, 7, 7, 7, 9, 7))
      inf60 &lt;- as.vector(c(1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 3, 2))
      sup60 &lt;- as.vector(c(5, 6, 6,  6,  8,  7,  7,  7,  7,  7,  7,  7,  8,  9,  8,  9,  9,  9, 11,  9))
      inf90 &lt;- as.vector(c(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 1, 1))
      sup90 &lt;- as.vector(c(10, 11, 11, 11, 15, 13, 13, 14, 12, 13, 13, 13, 14, 17, 15, 17, 17, 16, 21, 18))
  
  data &lt;- cbind.data.frame(Nb_obs, Nb_obst, inf20, sup20, inf40, sup40, inf60 , sup60, inf90 , sup90)
  </code></pre>
  
  <p>My plot : </p>
  
  <pre><code>plot(data$Nb_obst, data$Nb_obs, type = "n",  xlab = "Number obst", ylab = "number obs", ylim = c(0, 25))
  
  lines(data$Nb_obst, data$inf20, col = "dark red")
  lines(data$Nb_obst, data$sup20, col = "dark red")
  
  lines(data$Nb_obst, data$inf40, col = "red")
  lines(data$Nb_obst, data$sup40, col = "red")
  
  lines(data$Nb_obst, data$inf60, col = "dark orange")
  lines(data$Nb_obst, data$sup60, col = "dark orange")
  
  lines(data$Nb_obst, data$inf90, col = "yellow")
  lines(data$Nb_obst, data$sup90, col = "yellow")
  </code></pre>
  
  <p>My question : </p>
  
  <p>There are two things I'd like to do (and so I think it could be done by ggplot):</p>
  
  <p>In the idea of the graph at the top, the "inf" and "sup" are limits of my model in the IC 20%, then 40%, then 60%, and finally 90%. I would first like to smooth each curve, and then I would like to color the surface between two curves of the same IC, for example that the surface between "data$inf90" and "data$sup90" is yellow, the area between "data$inf60" and "data$60" is orange, etc. And I would like to superimpose each of these colored surfaces + put the good legend please. </p>
  
  <p>Thanks for your help !</p>