Install the package

install.packages("ggridges")

First try

library(ggplot2)
library(ggridges)
library(dplyr)
## 
## Attaching package: 'dplyr'
## The following objects are masked from 'package:stats':
## 
##     filter, lag
## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union
plt<-ggplot(iris, aes(x=Sepal.Width, y=Species, fill=Species))
plt<-plt+theme_bw()
plt+geom_density_ridges()
## Picking joint bandwidth of 0.13

Looks good, right.

Add data points

To do so, we will add rug lines at the bottom of each distribution, by turn on the option jittered_points.

plt<-plt+geom_density_ridges( # add rug points
    jittered_points = TRUE,
    position = position_points_jitter(width = 0.05, height = 0.01, yoffset = -0.1),
    point_shape = '|', point_size = 2, point_alpha = 0.8, alpha = 0.7, point_color="blue")
plt
## Picking joint bandwidth of 0.13

Parameter explanation:

• position_points_jitter() is used to determine where the rug lines are, here width and height gives the range for the lines to move randomly, and yoffset tells to move all lines downwards a certain amount.

• point_shape, point_size, point_alpha, point_color all determine the appearance of the rug lines.

Add the number of data points for each distribution

Get counts

pointCnt<-iris %>% group_by(Species) %>% count()

Update the plot with geom_text() to add counts.

plt+geom_text(data=pointCnt, aes(x=4.5, y=Species, label=n))
## Picking joint bandwidth of 0.13

Let’s move the count number a bit to the top

plt<-plt+geom_text(data=pointCnt, aes(x=4.5, y=Species, label=n),
  nudge_y = 0.95, vjust=1, size=7/.pt, color="red")
plt
## Picking joint bandwidth of 0.13

Here we use the parameter nudge_y to shift the y value upwards a certain amount and set text size and color.

It looks good, isn’t it?

References

One can find more examples of how to tune the ridgeline density plot at the following pages:

• https://r-charts.com/distribution/ggridges/

• https://wilkelab.org/ggridges/articles/introduction.html

• https://cran.r-project.org/web/packages/ggridges/vignettes/gallery.html

Happy programming 😄 !