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Learning D3.js Mapping

You're reading from   Learning D3.js Mapping Build stunning maps and visualizations using D3.js

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Product type Paperback
Published in Dec 2014
Publisher
ISBN-13 9781783985609
Length 126 pages
Edition 1st Edition
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Authors (2):
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Thomas Newton Thomas Newton
Author Profile Icon Thomas Newton
Thomas Newton
Oscar Villarreal Oscar Villarreal
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Oscar Villarreal
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Table of Contents (9) Chapters Close

Preface 1. Gather Your Cartographer's Toolbox FREE CHAPTER 2. Creating Images from Simple Text 3. Producing Graphics from Data – the Foundations of D3 4. Creating a Map 5. Click-click Boom! Applying Interactivity to Your Map 6. Finding and Working with Geographic Data 7. Testing Index

Experiment 2 – creating choropleths


One of the most common uses of D3.js maps is to make choropleths. This visualization gives you the ability to discern between regions, giving them a different color. Normally, this color is associated with some other value, for instance, levels of influenza or a company's sales. Choropleths are very easy to make in D3.js. In this experiment, we will create a quick choropleth based on the index value of the state in the array of all the states. Look at the following code or open up your browser to http://localhost:8080/chapter-4/example-3.html.

We will only need to modify two lines of code in the update section of our D3 code. Right after the enter section, add the following two lines:

  //Update
  var color = d3.scale.linear().domain([0,33]).range(['red', 'yellow']);
  mexico.attr('fill', function(d,i) {return color(i)});

The color variable uses another valuable D3 function named scale. Scales are extremely powerful when creating visualizations in D3; much...

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