r - ggplot set scale_color_gradientn manually

Question

I have a data frame like this

BP        R2      LOG10
96162057 0.2118000 2.66514431
96162096 0.0124700 0.31749391
96162281 0.0008941 0.07012148
96163560 0.5011000 2.48505399
96163638 0.8702000 3.37778598

and I want to plot BP against LOG10, and color the points by R2. R2 are continuous values from 0-1.

myplot <- read.cvs("mytable.csv",head=TRUE)
attach(myplot)
ggplot(myplot,aes(BP,LOG10, color=R2)) + geom_point() 

So far, so good. However I would like to display the R2 colors in manually selected intervals and colors, like this (if I had discrete values).

ggplot(myplot,aes(BP,LOG10, color=R2)) + geom_point() + 
      scale_color_manual(breaks= c("1","0.8","0.6","0.4","0.2","0"), 
                values = c("red","yellow","green","lightblue","darkblue"))
Error: Continuous value supplied to discrete scale

This looks pretty, but I would rather set the colors my self.

ggplot(myplot,aes(BP,LOG10, color=R2)) + geom_point(shape=1) + 
               scale_colour_gradientn(colours = rainbow(10))

So, how can I manually select intervals from continuous values (1-0.8, 0.8-0.6, 0.6-0.4, 0.4-0.2, 0.2-0), and color them to my liking (red, yellow, green, light, darkblue)? A smooth gradient between the colors would be cool, but not crucial.

Answer 1

You can use scale_colour_gradientn() and then provide your own colours= and values=. Values will give intervals for each color.

ggplot(myplot,aes(BP,LOG10, color = R2)) + geom_point() + 
  scale_colour_gradientn(colours = c("red","yellow","green","lightblue","darkblue"),
                         values = c(1.0,0.8,0.6,0.4,0.2,0))