Diagramming Data Flows: The Creative Art of Sankey Charts

Sankey diagrams, a visual tool used for depicting flows of goods, resources, energy or data between different points in a system, have gained widespread popularity in data visualization. These charts are named after Dr. John Sankey, an engineer who first used such diagrams in 1919 to visualize energy flows in steam engines. Today, Sankey diagrams are used across various fields, from energy auditing and industrial production to environmental analysis and social network analytics.

The Basics of Sankey Chart Creation

Creating a Sankey chart involves a few straightforward steps:

Identify the Inputs and Outputs: Begin with the starting point (input) and the end point (output). In an energy system, the inputs could be the different types of energy sources, and the outputs could be the various forms of energy used.
Determine the Flows: Once the inputs and outputs are identified, categorize the data flows between them. Sankey diagrams are most effective when data flows are clear and categorized.
Calculate the Scales: Determine the scale for the size of each arrow. In most cases, the scale is determined by the amount of data flowing through each link.
Create the Layout: Start creating the diagram with the largest flows and work your way down to the smaller ones. Leave enough space between each arrow for clarity.
Check the Overall Balance: Ensure the sum of all inputs equals the sum of all outputs. Sankey diagrams are a form of flow diagram reflecting conservation of mass.

Applications of Sankey Charts

Sankey diagrams are versatile and can be applied in a wide range of contexts:

Energy Consumption Analysis: They are extensively used for visualizing energy consumption patterns across industries and households, highlighting where energy efficiencies can be gained.
Network Traffic Analysis: Sankey diagrams can be used to visualize network traffic, helping network administrators understand traffic patterns and make informed decisions about optimization.
Food Supply Chains: In agriculture, Sankey diagrams can be employed to analyze the efficiency of food supply chains, revealing losses in transportation and storage processes.
Social Media Influence: By mapping follower flows between different social media accounts, businesses and marketers can understand the real impact of their social media strategies.

Creativity in Sankey Chart Design

While the underlying principle of Sankey diagrams remains consistent, the creativity and innovation in their design can make a significant difference in the impact they have. Designers can:

Adjust Arrow Widths: Instead of using static widths, designers can use arrow sizes to highlight specific data points, drawing viewer attention to critical areas.
Use Color Wisely: Different colors for inputs, outputs, or flows can enhance the clarity and readability of the chart.
Employ Symbols: Custom symbols for specific data flows can help in telling a specific story within the diagram.
Choose the Right Software: With the advent of powerful data visualization software and tools like Tableau, Microsoft PowerBI, and Python libraries like Altair, creators have more control over the appearance and customization of Sankey diagrams, leading to more engaging and informative visualizations.

Conclusion

Sankey diagrams are much more than just a method of visualizing data flow. They offer a creative canvas where data creators and data analysts can employ their skills to bring data to life. By skillfully using Sankey diagrams, anyone can tell compelling stories with data, making the complex understandable and the vast dataset digestible. As data analysis continues to evolve, so will the art of creating dynamic and insightful Sankey diagrams.

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