如何在ggplot2中添加与geom_hline相对应的图例（yintercept = log（2000））？

Question

我在ggplot2中使用geom_hline(yintercept = log(2000), linetype = "dotdash")在地图中添加y = log(2000)的水平线（附在下方）。

我想要的是在与虚线对应的y轴的左侧显示图例“log（2000）”。有什么想法吗？

情节的R代码如下：

library(ggplot2); library(scales) 
set.seed(10)
varx <- rep(c("group1", "group2"), each = 3)
vary <- rep(c("A", "B", "C"), 2)    
poi <- sample(20:30, 6)
upper <- sample(40:50, 6)
lower <- sample(1:10, 6)

dat <- data.frame(varx, vary, poi, upper, lower)
dat
#    varx vary poi upper lower
#1 group1    A  25    43     2
#2 group1    B  23    42     6
#3 group1    C  29    45     3
#4 group2    A  30    50     4
#5 group2    B  20    44     1
#6 group2    C  21    47    10

pp <- ggplot(dat, aes(colour = varx, y = poi, x = vary)) 

limits <- aes(ymax = upper, ymin = lower)

pp  + geom_point(aes(shape=varx), position = position_dodge(0.3), size = 2) + 
  ## dodge make the lines not stack upon each other
  geom_errorbar(limits, size = 1, width = 0.15, position = position_dodge(0.3)) + 
  theme_bw() + ## Get rid of the grey background
  geom_hline(yintercept = log(2000), linetype = "dotdash") +
  coord_cartesian(ylim = c(1, 60)) + 
  scale_shape_manual(values = c(17, 19)) + 
  theme(legend.justification= c(1, 0), 
        legend.position = c(1, 0.75),
        legend.key = element_blank(),## Get rid of the legend box 
        legend.title = element_blank(),
        legend.text = element_text(size = 10, face = "bold"),
        legend.background = element_rect(fill=alpha(0.0001))) +
  labs(x = NULL, y = NULL)

Answer 1

建立@ lukeA的评论

pp + scale_y_continuous(breaks = sort(c(log(2000), seq(0, 60, 10))),labels=c(0,"log(2000)",seq(10,60,10)))