rm(list=ls())

require(ggplot2)
require(sp)

set.seed(123456)
df=data.frame(x=runif(100,-1,1)
           ,y=runif(100,-1,1))
x=seq(-1,1,length=21)
Line1=data.frame(x=x,y=-0.5+0.8*x,g="L1")
Line2=data.frame(x=rev(x),y=0.5+0.6*rev(x),g="L2")
Linedf=rbind(Line1,Line2)
df$in.pg = ifelse(as.logical(point.in.polygon(df$x, df$y, pol.x=Linedf$x, pol.y=Linedf$y))
                  ,"Yes","No")
head(df)
ggplot()+
  geom_point(aes(x=x,y=y,colour=in.pg),data=df,inherit.aes = F)+
  geom_path(aes(x=x,y=y,group=g,colour=g),size=1.2,data=Linedf,inherit.aes = F)