Line Graphs - R Graphics - page 72

Making a Line Graph with Multiple Lines
Problem
You want to make a line graph with more than one line.
Solution
In addition to the variables mapped to the x- and y-axes, map another (discrete) variable to col-
our or linetype , as shown in Figure 4-6 :
# Load plyr so we can use ddply() to create the example data set
library(plyr)
# Summarize the ToothGrowth data
tg <- ddply(ToothGrowth, c( "supp" , "dose" ), summarise, length = mean(len))
# Map supp to colour
ggplot(tg, aes(x = dose, y = length, colour = supp)) + geom_line()
# Map supp to linetype
ggplot(tg, aes(x = dose, y = length, linetype = supp)) + geom_line()
Figure 4-6. Left: a variable mapped to colour; right: a variable mapped to linetype
Discussion
The tg data has three columns, including the factor supp , which we mapped to colour and
linetype :