Using Colors in Plots - R Graphics - page 323

Chapter12.Using Colors in Plots
In ggplot2's implementation of the grammar of graphics, color is an aesthetic, just like xposition,
yposition, and size. If color is just another aesthetic, why does it deserve its own chapter? The
reason is that color is a more complicated aesthetic than the others. Instead of simply moving
geoms left and right or making them larger and smaller, when you use color, there are many
degrees of freedom and many more choices to make. What palette should you use for discrete
values? Should you use a gradient with several different hues? How do you choose colors that
can be interpreted accurately by those with color-vision deficiencies? In this chapter, I'll address
these issues.
Setting the Colors of Objects
Problem
You want to set the color of some geoms in your graph.
Solution
In the call to the geom, set the values of colour or fill ( Figure 12-1 ):
ggplot(mtcars, aes(x = wt, y = mpg)) + geom_point(colour = "red" )
library(MASS) # For the data set
ggplot(birthwt, aes(x = bwt)) + geom_histogram(fill = "red" ), colour = "black"