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

Grouping

The group tag <g> is used often in SVG, especially in maps. It is used to group elements and then apply a set of attributes to that set. It provides the following benefits:

  • It allows you to treat a set of shapes as a single shape for the purpose of scaling and translating.
  • It prevents code duplication by allowing you to set attributes at a higher level and have them inherit all the elements included.
  • Groups are essential for applying transformations to large sets of SVG nodes in a performant manner. Grouping offsets the parent group rather than modifying each of the attributes in every item of the group.

Let's take the set of shapes used to explain Bézier curves and add all of them to a single group, combining everything we have learned so far, in the following code:

    <svg height="500" width="800"> 
      <g transform...