This page aims to describe how to build a basic circle packing chart with only one level of hierarchy. Basically, you just represent each entity or individual of your dataset with a circle, its size depending on a provided value.
It is like a barplot, but you use circle size instead of bar length. It is close to a bubble plot, but X and Y positions do not mean anything. It is a circle version of a treemap.
Calculating the arrangement of dots is not a trivial problem. The
packcircles library solves it and output coordinates of
every points of the circle edges.
Finally, ggplot2 allows to draw shapes thanks to
geom_polygon().
# Libraries
library(packcircles)
library(ggplot2)
# Create data
data <- data.frame(group=paste("Group", letters[1:20]), value=sample(seq(1,100),20))
# Generate the layout. This function return a dataframe with one line per bubble.
# It gives its center (x and y) and its radius, proportional of the value
packing <- circleProgressiveLayout(data$value, sizetype='area')
# We can add these packing information to the initial data frame
data <- cbind(data, packing)
# Check that radius is proportional to value. We don't want a linear relationship, since it is the AREA that must be proportionnal to the value
# plot(data$radius, data$value)
# The next step is to go from one center + a radius to the coordinates of a circle that
# is drawn by a multitude of straight lines.
dat.gg <- circleLayoutVertices(packing, npoints=50)
# Make the plot
ggplot() +
# Make the bubbles
geom_polygon(data = dat.gg, aes(x, y, group = id, fill=as.factor(id)), colour = "black", alpha = 0.6) +
# Add text in the center of each bubble + control its size
geom_text(data = data, aes(x, y, size=value, label = group)) +
scale_size_continuous(range = c(1,4)) +
# General theme:
theme_void() +
theme(legend.position="none") +
coord_equal()
