Circular Barplots and Customisation in R

In this article, we are going to see how to create Circular Barplots and Customisation in R Programming Language. 

A circular barplot is similar to a barplot, but instead of cartesian coordinates, it uses polar coordinates. A circular barplot is one in which the bars are presented in a circle rather than a line. This article will show you how to create such graphs using R and ggplot2. It contains reproducible code and explains how to use the coord_polar() method.

Define the data

To use dataset in barplot we need to create dataset so here we will create it.

R

# Libraries
library(tidyverse) # help you to prepare the data
library(ggplot2) # help you to prepare the plots

# prepare dataset
data = data.frame(
  # add a parameter with a range list 1-100
  index = seq(1,100),
  # create labelled parameter
  label = paste( data ="Data ",
                    seq(1,100),
                    sep="= "),
  # random values in the range 1 - 100
  values = sample( seq(10,100), 100, replace = T)
)

# top five values of the dataframe
head(data)

Output:

  index   label  values 
1     1 Data -1     28 
2     2 Data -2     46 
3     3 Data -3     54 
4     4 Data -4     25 
5     5 Data -5     43 
6     6 Data -6     26

Example 1: Basic Circular BarPlot

coord_polar() methods used to create plot in specific coordinated. 

Syntax:  coord_polar(theta = “x”, start = 0, direction = 1, clip = “on”)

Parameters: 

• theta: Variable to map angle to (x or y)
• start : Offset of starting point from 12 o’clock in radians. Offset is applied clockwise or anticlockwise depending on value of direction.
• direction : 1, clockwise; -1, anticlockwise
• clip : Should drawing be clipped to the extent of the plot panel? A setting of “on” (the default) means yes, and a setting of “off” means no. For details, please see coord_cartesian().

R

# Make the plot
p <- ggplot(data, aes(x = as.factor(index), # x-axis factor label

                      # y-axis numerical parameter
                      y = values)) +

  # the bar height will represent
  # the actual value of the data
  geom_bar(stat = "identity",
           fill=alpha("green", 0.5)) + # define bar color

  # define size of inner circle
  # and the size of the bar
  ylim(-100,120) +

  # define the polar coordinate
  coord_polar(start = 0)

# plot
p

Output:

Example 2: Adding labels to the data

To add labels and data into it will use geom_text() methods.

R

# Adding labels to the plot

data_with_labels = data

# number of labels required
number_of_label <- nrow(data_with_labels)
# find the angle of rotation of the label
angle <-  90 - 360 * (data_with_labels$index - 0.5) /number_of_label

# check the label alignment - right or left
data_with_labels$hjust<-ifelse( angle < -90, 1, 0)
# check the label angle
data_with_labels$angle<-ifelse(angle < -90,
                               angle + 180, angle)



# Make the plot
# x-axis factor label
p <- ggplot(data, aes(x = as.factor(index),

                      # y-axis numerical parameter
                      y = values)) +

  # the bar height will represent
  # the actual value of the data
  geom_bar(stat = "identity",

           # define bar color
           fill=alpha("green", 0.5)) +

  # define size of inner circle
  # and the size of the bar
  ylim(-100,120) +

  # define the polar coordinate
  coord_polar(start = 0) +

  # add labels
  geom_text(data = data_with_labels,
            aes(x = index, y = values+10,

                # label alignment
                label = label, hjust=hjust),
            color = "black", fontface="bold",
            alpha = 0.6, size = 2.5,
            angle = data_with_labels$angle,
            inherit.aes = FALSE )

p

Output: