Sankey charts are a type of data visualization that effectively represents flow data. The name Sankey comes from the inventor, Captain W.S. Sankey, who used them to illustrate steam flow through engineering plants and other processes in the late 19th century. However, they have evolved over time and are now widely used in various fields, from economics to environmental studies, to help us understand complex systems.

Understanding Sankey Charts

At their core, Sankey charts are visual representations that emphasize the movement of a quantity through a system. Each ‘sankey’ is a ‘ribbon’ or line that represents the size of the flow from one node (or endpoint) to another. The width of the ‘ribbons’ signifies the magnitude of the flow; this makes it easy to see which pathways carry a larger or smaller amount of flow.

Components of a Sankey Chart

1. Nodes or Origin Nodes – These are the starting points of the flow.
2. Terminal Nodes – These are the end points of the flow.
3. Links or Sankey – These represent the paths between nodes and the size of the flow through them.

Creating Sankey Charts

Creating a Sankey chart involves several steps, which can be done using various software tools from the simple to the complex:

1. Data Preparation: Organize your data in a format that includes:

   • Source nodes
   • Target nodes
   • Flow values (how much is moving from one node to another)
   • Additional category or flow detail (optional)

2. Choose a Tool: Select a tool based on user proficiency and requirement, such as:

   • Excel with PowerQuery add-ins
   • Google Sheets with Google Charts API
   • Data visualization software like Tableau, Plotly, or Python libraries such as Plotly and NetworkX

3. Input Data: Import your structured data into the chosen tool.

4. Design the Chart:

   • Position nodes based on category or sequence.
   • Arrange sankeys in a flowing pattern, indicating direction of flow.
   • Adjust the visual appearance, such as colors and labels, to improve readability and aesthetics.

5. Finalize and Publish: Review the chart for accuracy and clarity, then publish it for stakeholders or embed it into reports or presentations.

Applications of Sankey Charts

Sankey charts find applications in multiple fields:

1. Economics and Finance: They help in understanding financial flows, investments, and economic transactions.
2. Energy Systems: Representing energy consumption, production, and flow through different sources or systems.
3. Environmental Science: Tracking the flow of materials or gases through ecosystems or atmospheric systems.
4. Healthcare: Displaying the flow of treatments, patient movements between healthcare facilities, or drug usage across different groups.
5. Transportation: Illustrating traffic flow, goods movement, or passenger journeys in transportation networks.

Best Practices for Use

• Keep it Simple: Avoid overly complex charts with too many nodes and sankeys.
• Highlight Key Flows: Emphasize the most significant flows to draw attention to primary pathways or data points.
• Use Consistent Colors and Labels: This improves readability and the chart’s digestibility for a wide audience.
• Regular Updates: Frequently update the charts to include new data or changes in the system being measured.

Conclusion

Sankey charts are an invaluable tool for understanding complex flow dynamics in systems across various domains. Whether it’s tracking the movement of resources, data, or energy, these charts provide a visual representation that makes it easier to grasp the underlying patterns and significant pathways. By effectively creating and utilizing Sankey charts, professionals and data scientists can enhance decision-making across multiple industries by unlocking the inherent insights hidden within their data.

SankeyMaster

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