Weird behaviour of stat_bin position

Question

i am trying to overlay the percentage of people in the sample belonging to each bar, but i am not able to place the number on top of each bar. Even if I try to simply align each percentage with 0, the percentage of the first two bars are a little bit higher than the rest.

ggplot(bbdd, aes(t_fluoro)) +
    geom_histogram(breaks = seq(0, 30, by = 3.5), fill="#99ccff") + 
    scale_x_continuous(breaks=seq(0,30,by=3.5), limits=c(0,24.5), expand=c(0,0)) + 
    scale_y_continuous(limits=c(0,45), expand=c(0,0)) + 
    stat_bin(breaks = seq(0, 30, by = 3.5), 
           geom = "text", 
           color = "#333366",
           aes(y = after_stat(count / sum(count)), 
               label = scales::percent(after_stat(count / sum(count)))),
               vjust=0) +
    coord_fixed(ratio=0.6) +
    xlab(label = "Fluoroscopy time (min)") +
    ylab(label = "number of subjects") +
    theme_light()  +
    theme(panel.grid.minor = element_blank(),
          panel.grid.major.x = element_blank())

Thanks for the help!

I have tried several configs of Vjust and Hjust

Answer 1

In your code, simply change y = after_stat(count / sum(count)) to y = after_stat(count). Only use after_stat(count) as yparamater in aes to place the percentage labels on top

library(ggplot2)
library(scales)

set.seed(123) # For reproducibility
bbdd <- data.frame(
  t_fluoro = rnorm(100, mean = 12, sd = 5) # Generate 100 values with mean=12 and sd=5
)

ggplot(bbdd, aes(t_fluoro)) +
  geom_histogram(breaks = seq(0, 30, by = 3.5), fill="#99ccff") + 
  scale_x_continuous(breaks=seq(0,30,by=3.5), limits=c(0,24.5), expand=c(0,0)) + 
  scale_y_continuous(limits=c(0,45), expand=c(0,0)) + 
  stat_bin(breaks = seq(0, 30, by = 3.5), 
           geom = "text", 
           color = "#333366",
           aes(y = after_stat(count), # change made here
               label = scales::percent(after_stat(count / sum(count)))),
           vjust=-0.5) +
  coord_fixed(ratio=0.6) +
  xlab(label = "Fluoroscopy time (min)") +
  ylab(label = "number of subjects") +
  theme_light()  +
  theme(panel.grid.minor = element_blank(),
        panel.grid.major.x = element_blank())

Result:

I have tried several configs of Vjust and Hjust

vjust controls vertical justification

vjust=0.5 --> keeps the labels vertical position the same, 0 adjusted the labels up, 1 adjusts the labels down

hjust controls horizontal justification

hjust=0.5 --> keeps the labels horizontal position the same, 0 adjusted the labels to the right, 1 adjusts the labels to the left

See, how they work together: