向分类轴上的绘图添加垂直参考线

Question

In the plot below, I would like to add a custom error bar extending to the right of the bar. I'm halfway there, as shown below, in other words, I have the horizontal line, but I can't figure out how to add the vertical bar to the end of the skinny line as shown in green below. Does anyone have any ideas on how to accomplish this?

library(magrittr)
library(plotly)

df <- data.frame(grp = c("A", "B", "C", "D", "E") %>% as.factor,
           val = c(11:15)) %>% 
df %>%
  plot_ly(x = ~val,
          y = ~grp,
          type = "bar") %>% 
  add_segments(xend = 20,
               yend = ~grp)

Answer 1

You may add a marker to the end of the segment.
In addition you can group the legends of segement and marker together, so there are hidden/shown at the same time when toggling legend items.

Code

 df %>%
  plot_ly(x = ~val,
          y = ~grp,
          type = "bar") %>% 
  add_segments(xend = 20,
               yend = ~grp,
               legendgroup = "g1") %>%
  add_markers(x = 20,
              # style marker
              marker = list(
                symbol = "line-ns-open",
                size = 15,
                line = list(
                  width = 5
                )),
              # combine legends
              legendgroup = "g1",
              showlegend = F)
  

Plot