D3 Simple Gauge

A simple gauge written with D3.js that can be easily included in a project.

The base code was used from this example on CodePen and from this tutorial. I refactored the code of the example to make it work with D3.js v5, and I restructured the code to make it more flexible. Thanks to the original author (Jack Trent) for its work.

A demo of the gauge is available on my personal website.

Quick Start

The first step you need to do before to use the script is to include D3.js v5 in your project.

Once you have included D3 in your dependencies, you have the following options to use the script:

• Use the latest version of the master branch (see dist folder)
• Clone the repo: git clone https://github.com/antoinebeland/d3-simple-gauge.git
• Install with npm: npm install d3-simple-gauge

Be sure to include d3-simple-gauge.js file in your project before to start.

Usage

The gauge is very simple to use. You only have to initialize a new instance of the gauge with a configuration like in the following example to make it work. Once the gauge is initialized, you can set the percentage position of the needle with the percent or value properties.

const svg = d3.select('body')
  .append('svg')
  .attr('width', 400)
  .attr('height', 250);

const simpleGauge = new window.d3SimpleGauge.SimpleGauge({
  el: svg.append('g'),        // The element that hosts the gauge
  height: 200,                // The height of the gauge   
  interval: [0, 200],         // The interval (min and max values) of the gauge (optional)
  sectionsCount: 2,           // The number of sections in the gauge
  width: 400                  // The width of the gauge
});

setTimeout(() => {
  simpleGauge.percent = 0.7;  // The new percent of the needle to set (70%)
  
  setTimeout(() => {
    simpleGauge.value = 42;  // The new value of the needle to set inside the interval (21%)
  }, 1500);
}, 1500);

This script is written in ECMAScript 6 and is transpiled in UMD format. So, you can import it easily as a module. Look at the following examples to know how to import it:

// In an ES6 application
import { SimpleGauge } from './path/to/script/d3-simple-gauge';

// In the browser
const SimpleGauge = window.d3SimpleGauge.SimpleGauge

Configuration

The gauge can be easily customized with the following parameters when you create a new instance of SimpleGauge class. There are only four required parameters when you create a gauge. The others are optional (noted between []).

Name	Description
[animationDelay]	The delay in ms before to start the needle animation. By default, the value is 0.
[animationDuration]	The duration in ms of the needle animation. By default, the value is 3000.
[barWidth]	The bar width of the gauge. By default, the value is 40.
[easeType]	The ease type to use for the needle animation. By default, the value is d3.easeElastic.
el	The D3 element to use to create the gauge (must be a group or an SVG element).
height	The height of the gauge.
[interval]	The interval (min and max values) of the gauge. By default, the interval is [0, 1].
[needleColor]	The color to use for the needle.
[needleRadius]	The radius of the needle. By default, the radius is 15.
[percent]	The percentage to use for the needle position. By default, the value is 0.
[sectionsColors]	An array that contains the color to apply for each section.
sectionsCount	The number of sections in the gauge.
width	The width of the gauge.

Properties

Once the gauge is initialized, you can use the following properties to manipulate it.

Name	Description
interval	Gets or sets the interval of the gauge (min and max values).
percent	Gets or sets the percentage of the gauge. The percent must be between [0, 1].
value	Sets the needle position based on the specified value inside the interval. If the value specified is outside the interval, the value will be clamped to fit inside the domain.

Style

To apply colors on the gauge, you can specify them with the needleColor and sectionsColors properties in the configuration or with CSS classes.

If you choose to use needleColor and sectionsColors properties to set colors, be sure to specify these properties in the configuration like in the following example. Noted that the color specified should be a valid CSS color.

{
  // ...
  needleColor: 'black', // The needle color
  sectionsColors: [     // The color of each section
    'green',
    '#ffa500',
    'rgb(255, 0, 0)'
  ]
}

You can use CSS classes too to apply colors on the gauge. There are two classes used to set the needle colors (needle and needle-center), and there is one class for each group generated (chart-color{i}), where {i} is a number between 1 and the groups count, to apply a specific color to a group. You can take a look at the following example to know how to use these classes.

/* Fill color for the first group */
.chart-color1 {
  fill: #dea82c;
}

/* Fill color for the second group */
.chart-color2 {
  fill: #e9621a;
}

/* Fill color for the third group */
.chart-color3 {
  fill: #e92213;
}

/* Fill color for the needle */
.needle,
.needle-center {
  fill: #464A4F;
}

There are also other classes that can be used. Based on the percentage of the gauge, the arc points out by the needle has the active class. This can be useful if you want to apply a different style to the active group. Also, when the minimum (0%) or the maximum (100%) of the gauge are reached, the gauge element has min or max classes. Look at the following examples to know how to use these classes.

/* Put the active group always in black */
.arc.active {
  fill: #000;
}

/* When the gauge is at 0%, all the arcs appear blue */ 
.min .arc {
  fill: #00f;
}

/* When the gauge is at 100%, all the arcs appear red */
.max .arc {
  fill: #f00;
}

If you have used sectionsColor properties to set group colors, you have to add !important rule with the fill property if you want that active, min or max classes can be applied.

License

The code of this project is under MIT license.