This book explores the JavaScript library, D3.js, and its ability to help us create maps and amazing visualizations. You will no longer be confined to third-party tools in order to get a nice looking map. With D3.js, you can build your own maps and customize them as you please. This book will go from the basics of SVG and JavaScript to data trimming and modification with TopoJSON. Using D3.js to glue together these three key ingredients, we will create very attractive maps that will cover many common use cases for maps, such as choropleths, data overlays on maps, and interactivity.
Chapter 1, Gather Your Cartographer's Toolbox, covers the tools you need to install to build maps effectively with D3. We will cover the instructions to add NodeJS, npm, and TopoJSON to your system. This is needed in order to quickly bootstrap a local web server and to have the ability to manipulate map data.
Chapter 2, Creating Images from Simple Text, describes the basics of creating multiple shapes and designs with Scalable Vector Graphics (SVG).
Chapter 3, Producing Graphics from Data – the Foundations of D3, will deep dive into the main library of this book, D3.js. Concepts such as enter, update, and exit will be explained in detail with the use of some clever experiments and examples.
Chapter 4, Creating a Map, takes you through every step required to build a map with D3. Asynchronous loading of data, bounding box and projection creation, and TopoJSON element modification and data binding will be the bread and butter of this chapter.
Chapter 5, Click-click Boom! Applying Interactivity to Your Map, covers hover, panning, zooming, and their equivalent in touch events. Also, we'll dive into some nifty 3D projections, and a la par, we will learn transitions via experimentation.
Chapter 6, Finding and Working with Geographic Data, will take you through the process of acquiring data and optimizing it to your needs. This chapter covers one of the most important aspects of map visualization in detail via the use of TopoJSON.
Chapter 7, Testing, explains how to structure your codebase in order to have reusable chart components that are easily unit tested and primed for reuse in future projects.
The following are the requirements for this book; these work on OS X, Windows, and Linux:
A D3.js library v3.4.12
NodeJS v0.10.32
This book is carefully designed to allow the reader to jump between chapters based on what they are planning to get out of the book. Here is a brief guide to help you navigate the book:
In all cases, briefly read Chapter 1, Gather Your Cartographer's Toolbox, as it will provide a baseline on how your system is set up to easily follow the rest of the examples.
If you are new to SVG and D3, then read Chapter 2, Creating Images from Simple Text, and Chapter 3, Producing Graphics from Data – the Foundations of D3. Chapter 3, Producing Graphics from Data – the Foundations of D3, also provides a refresher to the enter, update, and exit pattern for those who have experience in D3.
If you are comfortable with all these basics and ready to jump into map creation immediately, then you can proceed directly to Chapter 4, Creating a Map, and Chapter 5, Click-click Boom! Applying Interactivity to Your Map. The examples should be easy to follow and help you get bootstrapped with map making quickly.
Once you are comfortable with map making, then Chapter 6, Finding and Working with Geographic Data, will help you further your craft by providing tools to help you work with the data.
If you are interested in testing D3 visualizations (not just maps), then read Chapter 7, Testing. It does not assume any prior map-making knowledge and can be read independently of chapters 4, 5, and 6.
Every chapter is full of pragmatic examples that can easily provide the foundation to more complex work. We have explained, step by step, how each example works. That said, we also firmly believe in "learning by doing". As you work through the examples, continue to experiment with the sample code provided. Change the data. Change the scaling functions and colors. See how the map reacts and play with D3. Most importantly, have fun!
In this book, you will find a number of styles of text that distinguish between different kinds of information. Here are some examples of these styles, and an explanation of their meaning.
Code words in text, database table names, folder names, filenames, file extensions, pathnames, dummy URLs, user input, and Twitter handles are shown as follows: "Then open your web browser to http://localhost:8080."
A block of code is set as follows:
<?xml version="1.0"?> <svg width="200" height="200"> <circle cx="60" cy="60" r="50"/> <circle cx ="5" cy="5" r="10" /> <circle cx="25" cy="35" r="45" /> <circle cx="180" cy="180" r="10"/> <circle cx="80" cy="130" r="40" /> <circle cx="50" cy="50" r="5" /> <circle cx="2" cy="2" r="7"/> <circle cx="77" cy="77" r="17"/> <circle cx="100" cy="100" r="40"/> <circle cx="146" cy="109" r="22"/> </svg>
Any command-line input or output is written as follows:
npm install -g http-server
New terms and important words are shown in bold. Words that you see on the screen, in menus or dialog boxes for example, appear in the text like this: "Click on the INSTALL button."
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