title: change the scale manually and legend labels to reflect intervals
body: <p>I have plotted a map in ggplot and used </p>
  
  <pre><code>library(ggplot2)
  library(maps)
  states &lt;- map_data("world")
  test&lt;-data.frame(Market=c("Fayzabad","Herat","Jalalabad","Kabul","Kandahar","Maymana","Mazar","Nili"),
               Country=rep("Afghanistan",8),lat=c(37.12144,34.34195,34.43419,34.52845,31.32000,35.92017,36.70000,33.72245),
               long=c(70.57852,62.20306,70.44768,69.17170,65.43000,64.77631,67.11667,66.12503),
               S=c(8.021731,9.002656,14.952483,9.201323,15.080901,15.009068,14.295761,6.217411),
               NC=c(2,3,3,5,3,2,6,9))
  
  
  p &lt;- ggplot()
  p &lt;- p + geom_polygon( data=states, aes(x=long, y=lat, group = group),fill="black",colour="white" )
  p &lt;- p + geom_point(data=test, aes(x=long, y=lat,color = S,size=NC))+
  scale_color_gradient(low="yellow",high="red", limit=c(0,25),space="Lab",name = "Seasonality")+
  
  scale_size(range = c(0, 10),name="Number of Commodities")+ggtitle("Seasonality Map")+theme_bw()
  p
  </code></pre>
  
  <p>which plots nicely the points I want on the map and gives a legend. However I would like to change the legend of the plot and set the color and size scale manually so that color and size scale and the legend look like...</p>
  
  <p>legend</p>
  
  <pre><code>NC
  *small circle*  1-3
  *medium circle* 4-6
  *large circle*  7-9
  
  S
  *yellow color*  &lt; 10
  *orange color*  10-25
  *red color*     25 &lt;
  </code></pre>
  
  <p>I know there is a cut function, but i just wanted to know if you can do it using the scale options in ggplot without making new categorical variables.</p>