向ggplot添加额外的图例，无需额外的包

Question

我有一个 ggplot，其中包含由线连接的不同主题（x 轴）的两组点。为他们创造了一个传奇。然后我想为每个科目添加点的变换，例如算术平均值，并获得一个单独的图例来解释附加点（这些点不是用线连接的）。

有没有办法在 ggplot 中做到这一点？

library(tidyverse)
y1 <- c(10,20,25)
y2 <- c(20,40,30)

adf <- data.frame(x=c('a','b','c'),y1=y1,y2=y2)

ldf <- adf |> pivot_longer(cols=c(y1,y2), names_to='ymethod',values_to='yval')

p <- ggplot(data=ldf)+
  geom_point(aes(x=x,y=yval, colour = ymethod)) +
  geom_line(aes(x=x,y=yval, colour = ymethod,group=ymethod))


# want an separate legend for these (points not joined by lines)
# called 'Mean' showing a single black point
p <- p+geom_point(data=adf|>mutate(am=0.5*(y1+y2)), 
                aes(x=x,y=am))

# doesn't do what I want
#p <- p+geom_point(data=adf|>mutate(am=0.5*(y1+y2)), 
#                  aes(x=x,y=am),col='black', show.legend = T) 

# doesn't do what I want
#p <- p+geom_point(data=adf|>mutate(am=0.5*(y1+y2)), 
#                  aes(x=x,y=am, col='black'), show.legend = T) 
  
# doesn't do what I want
#p <- p+geom_point(data=adf|>mutate(am=0.5*(y1+y2)), 
#                  aes(x=x,y=am, col='mean'), show.legend = T) +
#  scale_color_manual(values=c('mean'='black'))

print(p)

Answer 1

ggplot(data=ldf)+
  geom_point(aes(x=x,y=yval, colour = ymethod)) +
  geom_line(aes(x=x,y=yval, colour = ymethod,group=ymethod)) +
  geom_point(data=adf|>mutate(am=0.5*(y1+y2)), 
             aes(x=x,y=am, fill = "mean")) +
  guides(fill=guide_legend(title=element_blank()))

^{创建于 2024-11-07，使用 reprex v2.0.2}