abline 仅在 canvas 的箱线图中

Question

我想在箱线图中添加一个 abline()，但它绘制在整个图形中，而不仅仅是在 canvas 中。有解决方法吗？

boxplot(mpg ~ cyl, data = mtcars, main = "Car Milage Data",
        xlab = "Number of Cylinders", ylab = "Miles Per Gallon") 
abline(v = 2.5, col = "grey", lty = 2)

Answer 1

感谢Darren Tsai whose suggestion in :

Try par(xpd = F) and run your code again.

解决了问题。