Book Image

Learning D3.js 5 Mapping - Second Edition

By : Thomas Newton, Oscar Villarreal, Lars Verspohl
Book Image

Learning D3.js 5 Mapping - Second Edition

By: Thomas Newton, Oscar Villarreal, Lars Verspohl

Overview of this book

D3.js is a visualization library used for the creation and control of dynamic and interactive graphical forms. It is a library used to manipulate HTML and SVG documents as well as the Canvas element based on data. Using D3.js, developers can create interactive maps for the web, that look and feel beautiful. This book will show you how build and design maps with D3.js and gives you great insight into projections, colors, and the most appropriate types of map. The book begins by helping you set up all the tools necessary to build visualizations and maps. Then it covers obtaining geographic data, modifying it to your specific needs, visualizing it with augmented data using D3.js. It will further show you how to draw and map with the Canvas API and how to publish your visualization. By the end of this book, you'll be creating maps like the election maps and the kind of infographics you'll find on sites like the New York Times.
Table of Contents (13 chapters)
6
Finding and Working with Geographic Data

Experiment 3 – panning and zooming

A very common request when working with maps is to provide the ability to pan and zoom around the visualization. This is especially useful when a large map contains abundant detail. Luckily, D3 provides an event listener to help with this feature. In this experiment, we will outline the principles to provide basic panning and zooming for your map. This experiment requires us to start with example-1.html; however, feel free to look at http://localhost:8080/chapter-5/example-3.html for reference.

First, we will add a simple CSS class in our <style> section; this class will act as a rectangle over the entire map. This will be our zoomable area:

.overlay { 
  fill: none; 
  pointer-events: all; 
} 

Next, we need to define a function to handle the event when the zoom listener is fired. The following function can be placed right below...