# Gauge Charts in JavaScript

How to make a D3.js-based gauge chart in javascript.

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### Basic Gauge

A radial gauge chart has a circular arc, which displays a single value to estimate progress toward a goal. The bar shows the target value, and the shading represents the progress toward that goal. Gauge charts, known as speedometer charts as well. This chart type is usually used to illustrate key business indicators.

var data = [
{
domain: { x: [0, 1], y: [0, 1] },
value: 270,
title: { text: "Speed" },
type: "indicator",
mode: "gauge+number"
}
];

var layout = { width: 600, height: 500, margin: { t: 0, b: 0 } };
Plotly.newPlot('myDiv', data, layout);


### Add Steps, Threshold, and Delta

The following examples include "steps" attribute shown as shading inside the radial arc, "delta" which is the difference of the value and goal (reference - value), and "threshold" to determine boundaries that visually alert you if the value cross a defined threshold.

var data = [
{
domain: { x: [0, 1], y: [0, 1] },
value: 450,
title: { text: "Speed" },
type: "indicator",
mode: "gauge+number+delta",
delta: { reference: 380 },
gauge: {
axis: { range: [null, 500] },
steps: [
{ range: [0, 250], color: "lightgray" },
{ range: [250, 400], color: "gray" }
],
threshold: {
line: { color: "red", width: 4 },
thickness: 0.75,
value: 490
}
}
}
];

var layout = { width: 600, height: 450, margin: { t: 0, b: 0 } };
Plotly.newPlot('myDiv', data, layout);


### Custom Gauge Chart

var data = [
{
type: "indicator",
mode: "gauge+number+delta",
value: 420,
title: { text: "Speed", font: { size: 24 } },
delta: { reference: 400, increasing: { color: "RebeccaPurple" } },
gauge: {
axis: { range: [null, 500], tickwidth: 1, tickcolor: "darkblue" },
bar: { color: "darkblue" },
bgcolor: "white",
borderwidth: 2,
bordercolor: "gray",
steps: [
{ range: [0, 250], color: "cyan" },
{ range: [250, 400], color: "royalblue" }
],
threshold: {
line: { color: "red", width: 4 },
thickness: 0.75,
value: 490
}
}
}
];

var layout = {
width: 500,
height: 400,
margin: { t: 25, r: 25, l: 25, b: 25 },
paper_bgcolor: "lavender",
font: { color: "darkblue", family: "Arial" }
};

Plotly.newPlot('myDiv', data, layout);