下面举一个简单的小例子
library(ggplot2)
ggplot()+
annotate(geom = "segment",x=1,xend=1.5,y=1,yend=1)+
annotate...(geom = "segment",x=1,xend=1.5,y=2,yend=2)+
annotate(geom = "segment",x=1,xend=1,y=1,yend=2)+
annotate...(geom = "segment",x=1.5,xend=1.5,y=1,yend=2)+
annotate(geom = "segment",x=1,xend=1.5,y=1.5,yend=1.5