# Sunburst

Sunbursts are used to represent hierarchical information through a visualization showing hierarchy through a series of rings, that are sliced for each category node.  The central circle represents the root node, while the hierarchy moves outward from it, where each ring corresponds to a level in the hierarchy.

### Quick details

What: Discover Proportion

Why: Visually appealing way to understand hierarchies

## History of Sunburst

It is likely that the Sunburst Chart type of data visualization was developed to accommodate subunits of the Pie Chart’s primary segments. Sunbursts emerged as a variant of pie charts, which explains why they are also known as multilevel pies, or, simply, nested pie charts. The earliest known example of pie charts dates back to 1801, and it can be found in William Playfair’s Statistical Breviary.

Sunburst diagrams first published in Mechanical Engineering in 1921, showing the average annual net expenditure of the US federal government from 1910 to 1919

## When to Use a Sunburst?

### 1When many dimensions need to be represented in an easy to understand way

Use sunbursts when you need to represent many dimensions of data, unlike single dimension data which can be easily represented using a pie chart. In its structure, the rings are sliced up and divided based on their hierarchical relationship to the parent slice. The angle of each slice is either divided equally under its parent node or can be made proportional to a value. Because color can also be used to highlight hierarchal groupings or specific categories, sunbursts can be ideal to represent hierarchy in an easily consumable way.

First modern, computer-generated sunburst, based on the idea of a nested pie chart created by John Stasko in 2000

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### 2Compare more effectively, strengthening the existing proportional chart types, like pie, doughnut, and stacked column

Use a sunburst chart, to compare hierarchical data as a sunburst chart with multiple levels of categories shows how the outer rings relate to the inner rings. Also, there is definitely something aesthetically pleasing about circles making comparisons easier to make.  Various branches of an organization can be represented by designated hues, with different levels often taking on varying shades of the same color family. Rings can also be divided further to represent multiple divisions within the same organizational level.

Specialty Coffee Association of America’s Coffee Taster’s Flavor Wheel, 2016

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### 3Get at-a-glance breakdown of data in categories

Use Sunburst when required to add an additional dimension of depth to each parent branch. The Sunburst can unveil that the “parent” category has sub-categories that extend into specialty topics. In your work, use the uneven branching in a sunburst to emphasize and draw attention to a single slice, further teasing apart the contributions.

A multi-level pie chart(type of Sunburst), consisting of tiers, each layer representing a separate set of data.

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## Types of Sunburst

### 1. Treemap

This is a rectangular version of a radial sunburst. It is also used to represent hierarchical data however treemaps are split up into rectangles that are sized and ordered to indicate hierarchy

### 2. Multi-level pie chart

This chart consists of tiers, each layer representing a separate set of data. What would take three traditional pie graphs to illustrate, a multi-level pie graph can not only take the place of all three, but it also offers a clearer visual comparison.

## When not to use a Sunburst?

### 1When you need accurate comparison between hierarchical data

Treemaps, by their rectangular nature, are better suited for comparison among hierarchical levels as compared to sunbursts. This is so, because just as the way our minds differentiate size and shape, rectangles and straight lines are easier to compare than slices and angles. Specifically, rectangular treemaps, icicle charts and even bar charts, are much better for visualizing hierarchies than sunbursts.

### 2When you need visualization optimizing space in a better way

Do not use sunbursts when space is a constraint. Treemaps are here, optimized to show lots of data, because it stretches to within its bounding box, whereas plotting a Sunburst is fitting a circular chart into any rectangular window. In case of a sunburst, space that could be used to tell a story with your data is lost in the corners.