```#输入数据
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)
```#绘制图形
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="blue")
abline(h=c(30), lwd=1.5, lty=2, col="gray")
```#添加图例
legend("topleft", inset=.05, title="Drug Type", c("A","B"),lty=c(1, 2), pch=c(15, 17), col=c("red", "blue"))
```#图例似乎是太大了所以无法显示吗？我应该怎么处理呢？尝试了许多其他的图例代码都出现类似的结果，我看图例设置参数里面没有设置大小的参数呢？
