您可以使用geom_errorbar，其中ymin和ymax的值相同，如下所示：

library(ggplot2)
ggplot(aes(x = Factor, y = Percent), data = Tbl) + 
  geom_bar(position = "stack", stat = "identity", fill = "blue") +
  ylim(0,100) +
  geom_errorbar(aes(x = Factor, ymin = Percent, ymax = Percent), data = Tbl2,
                stat = "identity", color = "black") +
  theme_bw()

创建于2022年12月28日，使用reprex v2.0.2

另一个选项是带有shape = 95（线）的geom_point，并调整大小以适应：

library(tidyverse)

Tbl = data.frame(Factor = c("a","b","c","d"),
                 Percent = c(43,77,37,55))

Tbl2 = data.frame(Factor = c("a","b","c","d"),
                  Percent = c(58,68,47,63))

ggplot(aes(x = Factor, y = Percent), data = Tbl) + 
  geom_bar(position = "stack", stat = "identity", fill = "blue") +
  ylim(0,100) +
  geom_point(aes(x = Factor, y = Percent), data = Tbl2,
           position = "stack", stat = "identity", color = "black", shape = 95, size = 30) +
  theme_bw()

创建于2022年12月28日，使用reprex v2.0.2

下面是另一个使用geom_segment()的例子。有些人会说太花哨了，但无论如何：为此，我们必须扩展Tbl2：

library(ggplot2)
library(dplyr)

ggplot(aes(x = Factor, y = Percent), data = Tbl) + 
  geom_bar(position = "stack", stat = "identity", fill = "blue") +
  ylim(0,100) +
  geom_segment(data = Tbl2 %>% 
                 mutate(x = c(0.55, 1.55, 2.55, 3.55),
                        xend = x+0.9), aes(x=x,xend=xend, y = Percent, yend=Percent), size=2)+
  theme_bw()