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)

Use data attached to a visual element to affect its appearance

We can change attributes for a selection of DOM elements by passing static values, and all selected elements will have that attribute set to that one specific value. Add the following temporarily to the end of app.js:

d3.selectAll('circle').attr('cy', 300);

The following should be seen on your screen:

But now that each circle has one of our runs JavaScript data objects attached to it, we can set attributes on each circle using that data. We do that by passing the .attr() method a callback function instead of a static value for its second parameter. Remove d3.selectAll('circle').attr('cy', 300); and adjust the last line of app.js from d3.selectAll('circle').data(runs); to the following:

d3.selectAll('circle').data(runs)
    .attr('cy', function...