001、
library(ggplot2) p<-ggplot(mtcars,aes(mpg,hp,colour=factor(cyl)))+geom_point() p p+theme(axis.line.x=element_line(linetype=1,color="black",size=0.3))+ annotate(geom = 'segment', y = Inf, yend = -Inf, color = 'green', x = Inf, xend = Inf, size = 6) ## Inf无穷大, -Inf无穷小
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