Book Image

Learn Chart.js

By : Helder da Rocha
Book Image

Learn Chart.js

By: Helder da Rocha

Overview of this book

Chart.js is a free, open-source data visualization library, maintained by an active community of developers in GitHub, where it rates as the second most popular data visualization library. If you want to quickly create responsive Web-based data visualizations for the Web, Chart.js is a great choice. This book guides the reader through dozens of practical examples, complete with code you can run and modify as you wish. It is a practical hands-on introduction to Chart.js. If you have basic knowledge of HTML, CSS and JavaScript you can learn to create beautiful interactive Web Canvas-based visualizations for your data using Chart.js. This book will help you set up Chart.js in a Web page and show how to create each one of the eight Chart.js chart types. You will also learn how to configure most properties that override Chart’s default styles and behaviors. Practical applications of Chart.js are exemplified using real data files obtained from public data portals. You will learn how to load, parse, filter and select the data you wish to display from those files. You will also learn how to create visualizations that reveal patterns in the data. This book is based on Chart.js version 2.7.3 and ES2015 JavaScript. By the end of the book, you will be able to create beautiful, efficient and interactive data visualizations for the Web using Chart.js.
Table of Contents (14 chapters)
Title Page
Copyright and Credits
About Packt

Horizontal bar chart

When you have a lot of data to display and compare, it might fit better in a horizontal bar chart. You can easily convert a vertical bar chart into a horizontal one by changing the type to horizontalBar, as follows:

new Chart(ctx, {
    type: "horizontalBar",
    data: {…}

The preceding chart seems better as a horizontal chart, since the category labels don't have to be turned sideways. You can see the full code in Pages/BarChart10.html. The following screenshot shows what the chart looks like now:

A horizontal bar chart (code: Pages/BarChart10.html)

Adding extra datasets

You can add more datasets to a bar chart, and configure it with a new legend label, colors, and data arrays. In the following example, we will load a larger .csv file, which contains the data for plastic waste disposal in 2010, and a forecast for 2025. It has one extra column, as follows:

 United States...