Sankey charts are a powerful tool for visualizing flows and the movement of data or resources from one location to another. Created in 1898 by Scottish engineer and physicist Captain Topley Sankey, these charts have since become an essential part of data visualization, helping users to better understand complex systems and comprehend relationships and interactions within sets of data.
In this article, we will explore the concept of Sankey charts, how they are created, and provide examples of their applications in various industries, such as energy and resource management, social media analysis, and financial reporting.
The essence of Sankey charts
Sankey charts are designed to illustrate the flow or distribution of energy, data, or materials. They are particularly useful when trying to highlight the origin, movement, and destination of a resource. Instead of using a standard bar or line chart, Sankey diagrams use arrows, or “sankeys,” that are proportional in width to the quantity they represent. This visual representation makes it easy to identify heavy flows, bottlenecks, and the distribution of various sources among destinations.
Key elements of a Sankey diagram
- Nodes: These represent the entities in the system, such as sources, sinks, or locations where the flow starts or ends. Nodes are often displayed as rectangles, circles, or points.
- Links: These represent the flow of data, energy, or materials between two nodes. Links are the arrows that make up a Sankey diagram, and they can be directed or undirected.
- Width of links: The width of each link is proportional to the amount of flow it represents. This makes it easy to see which flows are more significant.
Designing a Sankey chart
- Data preparation: Gather the data that will be represented in the chart, including the origin, destination, and flow amount for each link.
- Node placement: Decide on the number and layout of the nodes. Nodes can be arranged based on categories or in a way that reflects the flow.
- Link visualization: Create the links between nodes, assigning appropriate colors and widths to represent the different attributes of the flows.
- Tuning and refinement: Adjust the layout, colors, and labels to ensure the chart is readable and highlights the key insights.
Applications of Sankey charts
Energy and resource management
Sankey charts can be used in various industries to show energy or resource consumption. For example, utilities companies can visualize the flow of electricity generated from different sources (e.g., coal, solar, wind) and its distribution to consumers. Energy audits and forecasts can be represented in a clear and accessible manner, allowing decision-makers to identify areas of improvement and potential bottlenecks.
Social media analysis
In marketing and community management, Sankey charts can be used to visualize the flow of interactions, such as user engagement on social media platforms. This can help companies understand which content or campaigns drive traffic, which types of interactions are most significant, and how different user segments contribute to these flows.
Financial reporting
Financial institutions leverage Sankey diagrams to visualize cash flows, including interbank transactions, investments, and returns. This helps in understanding how money moves within the organization or across sectors, highlighting potential opportunities for investment or areas requiring attention.
Health and epidemiology
A novel use of Sankey diagrams is in the visualization of disease spread within populations. By tracking the movement of individuals or the transmission of infections, public health professionals can identify hotspots, patterns of interaction, and potential containment strategies to mitigate the impact of outbreaks.
Creating a Sankey chart
To create a Sankey chart, you can utilize various visualization tools such as Tableau, Power BI, or specialized software like Vizzlo, Sankeymatic, and SankeyJS. These platforms offer templates, drag-and-drop functionality, and customization options to tailor your chart to your specific needs.
Best practices
- Limit the number of nodes: Too many nodes can make the chart cluttered and difficult to read. Aim for fewer nodes (ideally no more than 15) to maintain clarity.
- Consistent color use: Use a color scheme that clearly differentiates between nodes and maintains a visual hierarchy for the links.
- Label wisely: Provide clear labels for nodes, links, and tooltips to explain the data represented and guide the viewer through the chart.
- Focus on the key message: Highlight the most significant flows or patterns in the data to facilitate quick comprehension and insight discovery.
Unleashing the power of Sankey charts is about more than just creating appealing graphics. It’s about making complex data understandable, revealing insights, and supporting informed decision-making. With the right methods and tools, you can create Sankey diagrams that illuminate your data’s story and connect it to meaningful actions.
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