Book Image

HTML5 Graphing and Data Visualization Cookbook

By : Ben Fhala
Book Image

HTML5 Graphing and Data Visualization Cookbook

By: Ben Fhala

Overview of this book

The HTML5 canvas tag makes creating any plot shape easy, all you have to do then is fill it with exciting visualizations written in JavaScript or using other visualization tools. "HTML5 Graphing and Data Visualization Cookbook" is the perfect break into the world of Canvas, charts, and graphs in HTML5 and JavaScript. In this book we will go through a journey of getting to know the technology by creating and planning data-driven visualizations. This cookbook is organized in a linear, progressive way so it can be read from start to finish, as well as be used as a resource for specific tasks.This book travels through the steps involved in creating a fully interactive and animated visualization in HTML5 and JavaScript. You will start from very simple "hello world"ù samples and quickly dive deeper into the world of graphs and charts in HTML5. Followed by learning how canvas works and carrying out a group of tasks geared at taking what we learned and implementing it in a variety of chart types. With each chapter the content becomes more complex and our creations become more engaging and interactive.Our goal is that by the end of this book you will have a strong foundation; knowing when to create a chart on your own from scratch and when it would be a good idea to depend on other APIs.We finish our book in our last two chapters exploring Google maps and integrating everything we learnt into a full project.
Table of Contents (17 chapters)
HTML5 Graphing and Data Visualization Cookbook
About the Author
About the Reviewer

Creating a context-aware legend

Our goal will be to create a legend that updates based on what is under the user's mouse cursor as they roll over our application. Based on the mouse position of the user, we will update our legend to reflect the information that is under the user's mouse.

Getting ready

Grab the latest files from the previous recipe: 06.04.legend.html and 06.04.legend.js.

How to do it...

We aren't going to change anything in the HTML files so let's jump right into the JavaScript and build out our dynamic legend:

  1. From the ChartLine constructor, remove rollover/rollout events as we want to keep our legend always visible:

      this.mainDiv.onmousemove = this.bind(this,this.onMouseMoveArea);
      this.mainDiv.onmouseover = this.bind(this,this.fadeInLegend);
      this.mainDiv.onmouseout = this.bind(this,this.fadeOutLegend);
  2. Update the createLegend method:

    LineChart.prototype.createLegend = function (){
      var	can = document.createElement("canvas");