我如何在 R 中修复 plot 中的图例

Question

I run the following code:

plot(1:3, rnorm(3), pch = 1, lty = 1, type = "o", ylim=c(-2,2))
lines(1:3, rnorm(3), pch = 2, lty = 2, type="o")
legend(1,-1,c("group A", "group B"), pch = c(1,2), lty = c(1,2))

But the result I get is the following:

wrong legend

How can I fix the legend?

Answer 1

You gave the legend position as x=1, y=-1, in events that the points or lines are in that region it fails.

You have a few choices, either set the legend to top right, or you have to rescale you ylim in your case, sorry i don't have your seed so I cannot reproduce the plot. Or you can use the default "topleft","topright":

set.seed(100)
plot(1:3, rnorm(3), pch = 1, lty = 1, type = "o", ylim=c(-2,2))
lines(1:3, rnorm(3), pch = 2, lty = 2, type="o")
#legend(2.3,1.5,c("group A", "group B"), pch = c(1,2), lty = c(1,2))
legend("topleft",c("group A", "group B"), pch = c(1,2), lty = c(1,2))

This is the output I get

Answer 2

You need a legend out of the plot because your generating new plot after each run, use this

 plot(1:3, rnorm(3), pch = 1, lty = 1, type = "o", ylim=c(-2,2))
 lines(1:3, rnorm(3), pch = 2, lty = 2, type="o")
 legend("bottomright",c("group A", "group B"), pch = c(1,2), lty = c(1,2), inset=c(0,1), xpd=TRUE, horiz=TRUE, bty="n")

Here is the output