Radial tree
Encyclopedia
A radial tree, or "radial map", is a method of displaying a tree structure
(e.g., a tree data structure
) in a way that expands outwards, radially. It is one of many ways to visually display a tree., with examples extending back to the early 20th century. In use, it is a type of information graphic
.
Since the length of each orbit increases with the radius, there tends to be more room for the nodes. A radial tree will spread the larger number of nodes over a larger area as the levels increase. We use the terms level and depth interchangeably. Nevertheless, the number of nodes increases exponentially with the distance from the first node, whereas the circumference of each orbit increases linearly, so by the outer orbits, the nodes tend to be packed together.
There are a many extensions to this algorithm to create more visually balanced layouts, to allow a user to navigate from node to node (changing the center), or accommodate node labels and mix force-directed layouts with radial layouts.
The layout has some similarities to a hyperbolic tree, though a key difference is that hyperbolic trees are based on hyperbolic geometry
, whereas in a radial tree the distance between orbits is relatively linear.
Tree structure
A tree structure is a way of representing the hierarchical nature of a structure in a graphical form. It is named a "tree structure" because the classic representation resembles a tree, even though the chart is generally upside down compared to an actual tree, with the "root" at the top and the...
(e.g., a tree data structure
Tree (data structure)
In computer science, a tree is a widely-used data structure that emulates a hierarchical tree structure with a set of linked nodes.Mathematically, it is an ordered directed tree, more specifically an arborescence: an acyclic connected graph where each node has zero or more children nodes and at...
) in a way that expands outwards, radially. It is one of many ways to visually display a tree., with examples extending back to the early 20th century. In use, it is a type of information graphic
Information graphics
Information graphics or infographics are graphic visual representations of information, data or knowledge. These graphics present complex information quickly and clearly, such as in signs, maps, journalism, technical writing, and education...
.
Comparison to other layouts
In a simple case, the first node is at the top, and the linked nodes are beneath. As each node typically has more than one child, the resulting shape is relatively triangular. In a radial layout, instead of each successive generation being displayed a row below, each generation is displayed in a new, outer orbit.Since the length of each orbit increases with the radius, there tends to be more room for the nodes. A radial tree will spread the larger number of nodes over a larger area as the levels increase. We use the terms level and depth interchangeably. Nevertheless, the number of nodes increases exponentially with the distance from the first node, whereas the circumference of each orbit increases linearly, so by the outer orbits, the nodes tend to be packed together.
Basic layout
The overall distance "d" is the distance between levels of the graph, and is chosen so the overall layout will fit on a screen. Layouts are generated by working outward from the center, root. The first level is a special case because all the nodes have the same parent. The nodes for level 1 can be distributed evenly, or weighted depending on the number of children they have. For subsequent levels, the children are positioned within sectors of the remaining space, so that child nodes of one parent do not overlap with others.There are a many extensions to this algorithm to create more visually balanced layouts, to allow a user to navigate from node to node (changing the center), or accommodate node labels and mix force-directed layouts with radial layouts.
The layout has some similarities to a hyperbolic tree, though a key difference is that hyperbolic trees are based on hyperbolic geometry
Hyperbolic geometry
In mathematics, hyperbolic geometry is a non-Euclidean geometry, meaning that the parallel postulate of Euclidean geometry is replaced...
, whereas in a radial tree the distance between orbits is relatively linear.
Examples
- MindManagerMindManagerMindManager, called MindMan until version 3.5, is a commercial mind mapping software application developed by Mindjet Corporation. Mind maps created in MindManager are based on the mind mapping method by Tony Buzan. The latest version, MindManager 9, is available for Microsoft Windows...
and MindMapperMindMapperMindMapper is a Windows-based visual mapping software developed by SimTech Systems, that allows users to create mind maps, concept maps, flow charts, organizational charts, process maps, Gantt charts and Ishikawa diagrams. MindMapper offers integration with Microsoft Office and Unicode support...
are mindmappingMind mapA mind map is a diagram used to represent words, ideas, tasks, or other items linked to and arranged around a central key word or idea. Especially in British English, the terms spidergram and spidergraph are more common, but they can cause confusion with the term spider diagram used in mathematics...
systems, which can make radial-like layouts, though are not radial beyond the 2nd level. - SpicyNodesSpicyNodesIn concept mapping and information visualization, SpicyNodes is a method for displaying hierarchical data in which a focus node displays rich information, and the surrounding nodes display related information .- Main idea :...
is an approach to visualizing hierarchies, which allows moving from node to node.
External links
- Comprehensive survey and bibliography of Tree Visualization techniques
- Chris Harrison - WikiViz: Visualizing Wikipedia
- Radial maps at "Visual Complexity" site