r - 如何获取 geom_segment 显示图例

Question

下面的图有 2 个部分。

如何为线段添加图例？

理想情况下，最终结果有 2 个图例:

1. 其中一个是当前的“点图例”
2. 另一个图例是一个带有红色虚线标记为“段图例”的单个图例

这是代码

set.seed(11)
x = rnorm(100)

y = rnorm(100)

dat = data.frame(x = x, y = y)

ggplot(dat,aes(x=x,y=y)) + geom_point(aes(color="blue") ) +
  geom_segment(aes(x = -2, xend = 2, y = 0, yend = 2), color="red",  linetype="dashed", size=1.2) +
  geom_segment(aes(x = -1, xend = 1, y = -2, yend = -1), color="red",  linetype="dashed", size=1.2)   +
  scale_color_manual(name = "",values = c("blue"),labels="point legend")

Answer 1

#Generate data
x = rnorm(100)
y = rnorm(100)
dat = data.frame(x = x, y = y)

#Create new variable with same value as desired legend label
dat$cat<-rep('segment legend', 100) 
colnames(dat)<-c("x","y","segment legend") #change column name to legend label

#Plot
ggplot(dat,aes(x=x,y=y)) + geom_point(aes(color="blue") ) +
  geom_segment(aes(x = -2, xend = 2, y = 0, yend = 2, linetype=`segment legend`),
     color="red", size=1.2) + #move linetype= to inside aesthetics
  geom_segment(aes(x = -1, xend = 1, y = -2, yend = -1, linetype=`segment legend`), 
     color="red", size=1.2) + #move linetype= to inside aesthetics
  scale_color_manual(name = "",values = c("blue"),labels="point legend")+ 
  scale_linetype_manual("segment legend",values=c("segment legend"=2))+
  theme(legend.title=element_blank())