How to choose colors from a predefined set of colors in ggplot2

Question

Suppose I have a dataset, for example:

set.seed(1)
dataset <- data.frame(x = sort(rnorm(100)), 
                      y = sort(rlnorm(100))+1:4, 
                      group=rep(letters[1:4], 25))

I would like to create a graph using ggplot2. Instead of manually selecting colors, I use a predefined set of colors Paired:

ggplot(dataset, aes(x = x, colour = group)) + 
geom_line(aes(y=y)) + 
scale_colour_brewer(palette="Paired")

I get a graph as shown below: data points for groups aand bare located in two shades of blue, while the data points for groups cand dare located in two shades of green.

Suppose now that I would only like to build the data corresponding to the groups cand d, and I would like to use two shades of green. If I just do the following:

ggplot(dataset[dataset$group %in% c("c", "d"),], aes(x = x, colour = group)) + 
geom_line(aes(y=y)) + 
scale_colour_brewer(palette="Paired")

(. ), Paired.

, : , ggplot2

Answer 1

require(RColorBrewer)
ggplot(dataset[dataset$group %in% c("c", "d"),], aes(x = x, colour = group)) + 
  geom_line(aes(y=y)) + 
  scale_colour_manual(values = brewer.pal(4, "Paired")[3:4])

, . .