How to plot stacked area chart in R?
This recipe helps you plot stacked area chart in R
Recipe Objective
A stacked area chart is a type of area graph which showcases the evolution of a specific numeric value amongst different groups in a single graph. These specific values are stacked on top of each other for each group which allows us to witness the evolution of the total value as well as the importance of a group.
In this recipe we are going to use ggplot2 package to plot the required stacked area Chart. ggplot2 package is based on the book "Grammar of Graphics" by Wilkinson. This package provides flexibility while incorporating different themes and plot specification with a high level of abstraction. The package mainly uses aesthetic mapping and geometric objects as arguments. Different types of geometric objects include:
- geom_point() - for plotting points
- geom_bar() - for plotting bar graph
- geom_line() - for plotting line chart
- geom_histogram() - for plotting histogram
The basic syntax of gggplot2 plots is:
ggplot(data, mapping = aes(x =, y=)) + geometric object
where:
- data : Dataframe that is used to plot the chart
- mapping = aes() : aesthetic mapping which deals with controlling axis (x and y indicates the different variables)
- geometric object : Indicates the code for typeof plot you need to visualise.
This recipe demonstrates how to make a stacked area chart using ggplot2.
STEP 1: Loading required library and dataset
Dataset description: It is the basic data about the customers going to the supermarket mall. The variable that we interested in is Annual.Income which is in 1000s and Spending Score
# Data manipulation package
library(tidyverse)
# ggplot for data visualisation
library(ggplot2)
# reading a dataset
customer_seg = read.csv('Mall_Customers.csv')
glimpse(customer_seg)
Rows: 200 Columns: 5 $ CustomerID1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 1... $ Gender Male, Male, Female, Female, Female, Female, ... $ Age 19, 21, 20, 23, 31, 22, 35, 23, 64, 30, 67, ... $ Annual.Income..k.. 15, 15, 16, 16, 17, 17, 18, 18, 19, 19, 19, ... $ Spending.Score..1.100. 39, 81, 6, 77, 40, 76, 6, 94, 3, 72, 14, 99,...
STEP 2: Plotting a Stacked area chart using ggplot
We use geometric object as geom_area() and adding another categorical variable in the fill arguement under mapping.
Note:
- The + sign in the syntax earlier makes the code more readable and enables R to read further code without breaking it.
- We also use labs() function to give a title to the graph
ggplot(df, mapping = aes(x = year,y = Amount_USD, fill = factor(type_of_expense))) +
geom_area()+
labs(title="Expenses of Students")
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