1 dose <- c(20, 30, 40, 45,60)
 2 drugA <- c(16, 20, 27, 40, 60)
 3 drugB <- c(15, 18, 25, 31, 40) # 数据准备
 4 
 5 opar <- par(no.readonly=T) # 保存画图环境
 6 
 7 par(lwd=2, cex=1.5, font.lab=2) # 设置画图环境
 8 plot(dose, drugA, type="b", pch=15, lty=1, col="red", ylim=c(0,60), main="Drug A vs. Drug B",
 9      xlab="Drug Dosage", ylab="Drug Response") # 画药物A
10 lines(dose, drugB, type="b", pch=17, lty=2, col="blue") # 在原来的图形上画药物B
11 
12 abline(h=c(30), lwd=1.5, lty=2, col="grey") # 添加水平参考线x=30
13 
14 install.packages("Hmisc") # 安装坐标轴精度的packages
15 library(Hmisc)
16 
17 minor.tick(nx=3, ny=3, tick.ratio=0.5) # 设置次要刻度线是主刻度线的一半
18 
19 legend("topleft", inset=.05, title="Drug Type", c("A", "B"),
20        lty=c(1,2), pch=c(15,17), col=c("red", "blue")) # 添加图例
21 
22 par(opar) #恢复原来的图形环境