Sankey diagram
Description
Sankey diagrams are a type of flow diagram that shows movement direction and flow quantity through arrows or lines. The width of the arrow or line shows magnitude; the thicker the arrow or line, the larger the quantity of flow. Flow arrows or lines can combine or separate their paths as they move along a process, and colours may be used to show different categories of movement or to divide different stages in a process.
When to use
Sankey Diagrams are commonly used to visually show the movement of population from one place to another, but they can also be used to show the flow of any isolated system process.
Dos and donts
Use distinct colours to group the entities into different categories, which helps in making comparisons and distinguishing groups.
Apply transparency to the colours.
Avoid using Sankey diagrams when the flows have similar values (widths) as it can make it difficult to differentiate and compare. If these comparisons are essential for your purpose, consider a (stacked) bar chart.
- Keep it simple. Since not everyone is familiar with this visualization type, complex Sankey diagrams may require explanation.
- Minimise the number of crossing arcs by carefully ordering the groups on either side of the diagram.
Chord diagram
Description
Chord diagrams visualize flows and relationships between multiple entities. Entities are arranged radially around a circle, with the relationships between them connected to each other using arcs. Values are assigned to each connection, which is represented proportionally by the size of each arc.
When to use
Chord diagrams can be used to show the flows and relationship between the datasets such as displacement of refugees from one country to another. Chord diagrams are eye-catching which makes them popular among different visualization types. However, they could become quickly cluttered and unreadable when visualizing larger datasets.
Dos and donts
Apply transparency to the colours.
Use distinct colours to group the entities into different categories, which helps in making comparisons and distinguishing groups.
- Minimize the number of crossing arcs, by carefully ordering groups around the circle.
- Keep it simple. Since not everyone is familiar with this visualization type, complex chord diagrams may require explanation.
Flow map
Description
Flow maps show the flow of objects from one geographical location to another and their quantity. The arrows show direction, while the width illustrates the quantity. This helps to show how objects move geographically.
When to use
Flow maps are most frequently used to show the movement of population, but also animal migrations, money flow, the traffic of goods, etc.
Dos and donts
Use curved lines to show movement instead of straight lines.
Use headed arrows.
Make the arrows’ width proportional to flow rate.
Make sure flows and arrowheads don’t overlap.
Tools available
Illustrator GIS
Arc diagram
Description
Arc diagrams are two-dimensional informative network diagrams showing the connection and flow between entities (nodes). It consists of two elements i.e. nodes and links. Nodes represent the entities of the data. It is presented on a single horizontal line (a one-dimensional axis). Arcs are used as links intended to show flow or connection between the nodes. The width of the arc line and the size of nodes can be used to add further details such as quantity or frequency of connection or movement between entities.
When to use
Arc Diagrams are ideal for visualizing networks, connections, and flow between different entities of information and the distribution of connections.
Dos and donts
Don’t use arc diagrams when there are too many links as it might make the diagram too cluttered to understand.
- Don’t use arc diagrams to show the exact structure or connections between nodes.
Flow diagram
Description
Flow charts show the sequential steps of a defined process. Flow charts can effectively simplify complex or abstract procedures for communication. The process is mapped out using connected symbols, such as arrows, indicating the direction of the next step. Boxes around steps sometimes use different shapes to differentiate the type of step. These symbols are standardized in order to make interpretation of these charts easier. Details of each step are written within the symbols to clarify and explain the process.
When to use
Flow charts are widely used in multiple fields to document, study, plan, improve and communicate complex processes in clear, easy-to-understand diagrams.
Dos and donts
Use consistent design elements (shapes, lines and texts) within a flowchart.
Flow data from left to right.
- Keep it simple and avoid complicated flow charts (one-page maximum).