library(ggplot2)
ggplot(pressure, aes(x=temperature, y=pressure)) +
geom_line() +
geom_point() +
geom_line(mapping = aes(y=pressure/2, colour="red")) +
geom_point(mapping = aes(y=pressure/2), colour="red")
library(ggplot2)
ggplot(pressure, aes(x=temperature, y=pressure)) +
geom_line() +
geom_point() +
geom_line(mapping = aes(y=pressure/2, colour="red")) +
geom_point(mapping = aes(y=pressure/2), colour="red")