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
Contributors
Preface
Index

Configuring scales


A scale is a transformation that enlarges or shrinks a data domain so that it fits a specific range. Chart.js scales data automatically, adjusting domain data values so they fit within the space reserved for the chart. A scale is represented by an axis, which is a directed line that represents the extent of the domain. The discrete values that are placed on an axis line are called ticks. A coordinate system with perpendicular or radial axes and discrete ticks forms a grid. Scales, axes, ticks, and grids exist in all charts, even if you don’t see them. They control how the data points will be displayed in the chart.

Cartesian charts have two scales, each represented by perpendicular axes, x and y, and radial charts have one scale, represented by the radius and angle. Radial scales are always linear, but Cartesian scales can be linear, logarithmic, categorical, or temporal. Chart.js also allows you to create your own scales.

In most charts, the axes, grid lines, and tick labels...