Background

Let’s visualize the quantiles of a normal distribution using a density plot.

Setup

library(tidyverse)

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library(gganimate)
set.seed(123)

Simulate normal data

n <- 1e4
data <- data.frame(x = rnorm(n))
data$decile <- cut(data$x, breaks = quantile(data$x, probs = seq(0, 1, 0.1)), include.lowest = TRUE)
data$decile2 <- cut(data$x, breaks = quantile(data$x, probs = seq(0, 1, 0.1)), include.lowest = TRUE, labels = 1:10)

Using decile and decile2 we have marked for each data point to which decile it belongs.

Build up the data frame

data2 <-
  data |> 
  group_by(decile2) |> 
  mutate(x_max = max(x)) 

data3 <-
  data2 |> 
  ungroup() |> 
  select(x)

And plot:

p <- 
  ggplot(data2, aes(x = x)) +
  geom_density(data = data3, fill = "grey", alpha = .5, color = NA) +
  geom_vline(aes(xintercept = x_max)) +
  geom_label(aes(label = decile2, x = x_max), y= 0) +
  theme_minimal()
p