源代码：
dose <- c(20, 30, 40, 45, 60)
drugA <- c(16, 20, 27, 40, 60)
drugB <- c(15, 18, 25, 31, 40)
opar <- par(no.readonly = TRUE)
par(lwd = 2, cex = 1.5, font.lab = 2)
plot(dose, drugA, type = "b",
pch = 15, lty = 1, col = "red", ylim = c(0, 60),
main = "Drug A vs. Drug B",
xlab = "Drug Dosage", ylab = "Drug Response")
lines(dose, drugB, type = "b",
pch = 17, lty = 2, col = "gray")
library(Hmisc)
mirror.tick(nx = 3, ny = 3, tick.radio = 0.5)
legend("topleft", inset = .05, title = "Drug Type", c("A", "B"),
lty = c(1,2), pch = c(15, 17), col = c("red", "blue"))
par(opar)
显示效果：