Adding boxplot below density plot - r

Question

I'm new to ggplot and I'm trying to create this graph:
But actually, I'm just stuck here:
This is my code :
ggplot(diamonds) +
aes(x = carat, group = cut) +
geom_line(stat = "density", size = 1) +
theme_grey() +
facet_wrap(~cut, nrow = 5, strip.position = "right") +
geom_boxplot(aes())
Does someone know what I can do next?

Answer 1

Edit: As of ggplot2 3.3.0, this can be done in ggplot2 without any extension package.
Under the package's news, under new features:
All geoms and stats that had a direction (i.e. where the x and y axes
had different interpretation), can now freely choose their direction,
instead of relying on coord_flip(). The direction is deduced from
the aesthetic mapping, but can also be specified directly with the new
orientation argument (#thomasp85, #3506).
The following will now work directly (replacing all references to geom_boxploth / stat_boxploth in the original answer with geom_boxplot / stat_boxplot:
library(ggplot2)
ggplot(diamonds, aes(x = carat, y = -0.5)) +
# horizontal boxplots & density plots
geom_boxplot(aes(fill = cut)) +
geom_density(aes(x = carat), inherit.aes = FALSE) +
# vertical lines at Q1 / Q2 / Q3
stat_boxplot(geom = "vline", aes(xintercept = ..xlower..)) +
stat_boxplot(geom = "vline", aes(xintercept = ..xmiddle..)) +
stat_boxplot(geom = "vline", aes(xintercept = ..xupper..)) +
facet_grid(cut ~ .) +
scale_fill_discrete()
Original answer
This can be done easily with a horizontal boxplot geom_boxploth() / stat_boxploth(), found in the ggstance package:
library(ggstance)
ggplot(diamonds, aes(x = carat, y = -0.5)) +
# horizontal box plot
geom_boxploth(aes(fill = cut)) +
# normal density plot
geom_density(aes(x = carat), inherit.aes = FALSE) +
# vertical lines at Q1 / Q2 / Q3
stat_boxploth(geom = "vline", aes(xintercept = ..xlower..)) +
stat_boxploth(geom = "vline", aes(xintercept = ..xmiddle..)) +
stat_boxploth(geom = "vline", aes(xintercept = ..xupper..)) +
facet_grid(cut ~ .) +
# reproduce original chart's color scale (o/w ordered factors will result
# in viridis scale by default, using the current version of ggplot2)
scale_fill_discrete()
If you are limited to the ggplot2 package for one reason or another, it can still be done, but it would be less straightforward, since geom_boxplot() and geom_density() go in different directions.
Alternative 1: calculate the box plot's coordinates, & flip them manually before passing the results to ggplot(). Add a density layer in the normal way:
library(dplyr)
library(tidyr)
p.box <- ggplot(diamonds, aes(x = cut, y = carat)) + geom_boxplot()
p.box.data <- layer_data(p.box) %>%
select(x, ymin, lower, middle, upper, ymax, outliers) %>%
mutate(cut = factor(x, labels = levels(diamonds$cut), ordered = TRUE)) %>%
select(-x)
ggplot(p.box.data) +
# manually plot flipped boxplot
geom_segment(aes(x = ymin, xend = ymax, y = -0.5, yend = -0.5)) +
geom_rect(aes(xmin = lower, xmax = upper, ymin = -0.75, ymax = -0.25, fill = cut),
color = "black") +
geom_point(data = . %>% unnest(outliers),
aes(x = outliers, y = -0.5)) +
# vertical lines at Q1 / Q2 / Q3
geom_vline(data = . %>% select(cut, lower, middle, upper) %>% gather(key, value, -cut),
aes(xintercept = value)) +
# density plot
geom_density(data = diamonds, aes(x = carat)) +
facet_grid(cut ~ .) +
labs(x = "carat") +
scale_fill_discrete()
Alternative 2: calculate the density plot's coordinates, & flip them manually before passing the results to ggplot(). Add a box plot layer in the normal way. Flip the whole chart:
p.density <- ggplot(diamonds, aes(x = carat, group = cut)) + geom_density()
p.density.data <- layer_data(p.density) %>%
select(x, y, group) %>%
mutate(cut = factor(group, labels = levels(diamonds$cut), ordered = TRUE)) %>%
select(-group)
p.density.data <- p.density.data %>%
rbind(p.density.data %>%
group_by(cut) %>%
filter(x == min(x)) %>%
mutate(y = 0) %>%
ungroup())
ggplot(diamonds, aes(x = -0.5, y = carat)) +
# manually flipped density plot
geom_polygon(data = p.density.data, aes(x = y, y = x),
fill = NA, color = "black") +
# box plot
geom_boxplot(aes(fill = cut, group = cut)) +
# vertical lines at Q1 / Q2 / Q3
stat_boxplot(geom = "hline", aes(yintercept = ..lower..)) +
stat_boxplot(geom = "hline", aes(yintercept = ..middle..)) +
stat_boxplot(geom = "hline", aes(yintercept = ..upper..)) +
facet_grid(cut ~ .) +
scale_fill_discrete() +
coord_flip()

Answer 2

Maybe this will help. Although need little upgrade :)
library(tidyverse)
library(magrittr)
library(wrapr)
subplots <-
diamonds$cut %>%
unique() %>%
tibble(Cut = .) %>%
mutate(rn = row_number() - 1) %$%
map2(
.x = Cut,
.y = rn,
~annotation_custom(ggplotGrob(
diamonds %>%
filter(cut == .x) %.>%
ggplot(data = .) +
aes(x = carat, fill = cut) +
annotation_custom(ggplotGrob(
ggplot(data = .) +
geom_boxplot(
aes(x = -1, y = carat),
fill = .y + 1
) +
coord_flip() +
theme_void() +
theme(plot.margin = margin(t = 20))
)) +
geom_line(stat = 'density', size = 1) +
theme_void() +
theme(plot.margin = margin(t = .y * 100 + 10, b = (4 - .y) * 100 + 40))
))
)
ggplot() + subplots