Book Image

D3.js Quick Start Guide

By : Matthew Huntington
Book Image

D3.js Quick Start Guide

By: Matthew Huntington

Overview of this book

D3.js is a JavaScript library that allows you to create graphs and data visualizations in the browser with HTML, SVG, and CSS. This book will take you from the basics of D3.js, so that you can create your own interactive visualizations, to creating the most common graphs that you will encounter as a developer, scientist, statistician, or data scientist. The book begins with an overview of SVG, the basis for creating two-dimensional graphics in the browser. Once the reader has a firm understanding of SVG, we will tackle the basics of how to use D3.js to connect data to our SVG elements. We will start with a scatter plot that maps run data to circles on a graph, and expand our scatter plot to make it interactive. You will see how you can easily allow the users of your graph to create, edit, and delete run data by simply dragging and clicking the graph. Next, we will explore creating a bar graph, using external data from a mock API. After that, we will explore animations and motion with a bar graph, and use various physics-based forces to create a force-directed graph. Finally, we will look at how to use GeoJSON data to create a map.
Table of Contents (10 chapters)

Creating a zoom behavior that scales elements

Another behavior we can create is the zooming/panning ability. Once this functionality is complete, you will be able to zoom in and out on different parts of the graph by doing one of the following:

  • A two-finger drag on a trackpad
  • Rotating your mouse wheel
  • Pinching/spreading on a trackpad

You will also be able to pan left, right, up, and down on the graph by clicking and dragging on the SVG element.

Put the following code at the bottom of app.js:

var zoomCallback = function(){
d3.select('#points').attr("transform", d3.event.transform);
}

This is the callback function that will be called when the user attempts to zoom or pan. All it does is take the zoom or pan action and turn it into a transform attribute that gets applied to the <g id="points"></g> element that contains the circles. Now...