Several distributions in the same plot -- using geom_density function from ggplot2

Question

I think I'm very close to getting this code done, but I'm missing something here. I want to "combine" two plots into just one like this:

The first plot has this code:

  ggplot(test, aes(y=key,x=value)) + 
  geom_path()+
  coord_flip()

And the second one has this one below:

  ggplot(test, aes(x=value, fill=key)) +
  geom_density() +
  coord_flip()

This kind of multiple distributions plot are often seen in stats book when we read about normal distributions. The most useful link I've got so far was this one here.

Please use this code to reproduce my question:

library(tidyverse)
test <- data.frame(key = c("communication","gross_motor","fine_motor"),
                   value = rnorm(n=30,mean=0, sd=1))
ggplot(test, aes(x=value, fill=key)) +
  geom_density() +
  coord_flip()

ggplot(test, aes(y=key,x=value)) + 
  geom_path(size=2)+
  coord_flip()

Thanks much

Answer 1

You might be interested in ridgeline plots from the ggridges package.

Ridgeline plots are partially overlapping line plots that create the impression of a mountain range. They can be quite useful for visualizing changes in distributions over time or space.

library(tidyverse)
library(ggridges)

set.seed(123)
test <- data.frame(
  key = c("communication", "gross_motor", "fine_motor"),
  value = rnorm(n = 30, mean = 0, sd = 1)
)

ggplot(test, aes(x = value, y = key)) + 
  geom_density_ridges(scale = 0.9) + 
  theme_ridges() +
  NULL
#> Picking joint bandwidth of 0.525

Add median line:

ggplot(test, aes(x = value, y = key)) +
  stat_density_ridges(quantile_lines = TRUE, quantiles = 2, scale = 0.9) +
  coord_flip() +
  theme_ridges() +
  NULL
#> Picking joint bandwidth of 0.525

Simulate a rug:

ggplot(test, aes(x = value, y = key)) + 
  geom_density_ridges(
    jittered_points = TRUE,
    position = position_points_jitter(width = 0.05, height = 0),
    point_shape = '|', point_size = 3, point_alpha = 1, alpha = 0.7,
  ) +
  theme_ridges() +
  NULL
#> Picking joint bandwidth of 0.525

^{Created on 2018-10-16 by the reprex package (v0.2.1.9000)}