Decoding Complexity with Sankey Diagrams: A Comprehensive Guide to Visualizing Flows and Energies in Systems
Sankey diagrams have been a favorite tool for presenting the flow of information, money, material, energy, and other resources since the renowned Scottish engineer and physicist, Peter Henry Gustav Sander, introduced them in 1857. These diagrams provide an intuitive and comprehensive way to visualize the magnitude of exchanges between different components, making it easier to comprehend systems with multiple interacting parts, complex flows, and hierarchical data. In this article, we delve into the intricacies of Sankey diagrams, their application, strengths, and limitations, and step-by-step guide on how to create compelling Sankey diagrams using popular data visualization tools.
Understanding the Mechanics of Sankey Diagrams:
At the heart of a Sankey diagram lies the concept of “Sankey flow,” which represents the quantity passed between two elements in a system. The width of the flow bands directly correlates with the magnitude of the passed quantity – wider the bands, more significant the flow. The arrows on a Sankey diagram, sometimes in both directions for two-way flows, show the direction of the flow.
A distinguishing feature of Sankey diagrams is their layout. The diagram typically starts from the top with elements representing sources, from where the flow originates, while the receiving elements are placed at the bottom. Each flow is a path in this layout, potentially connecting multiple source and receptor elements, which enables the display of flows within flows or multiple sources and receivers.
Strengths of Sankey Diagrams:
1. Visual Clarity: Sankey diagrams offer a clear and easily digestible visual presentation of complex relationships, making them ideal for situations where many connected parts need to be understood at a glance.
2. Quantitative Detail: The width of the bands in Sankey diagrams allows precise quantification and comparison of flow amounts, crucial for understanding the proportional importance of different components in the system.
3. Hierarchical Presentation: The layout of Sankey diagrams naturally creates a hierarchical structure, making it easy to identify high-level relationships, secondary dependencies, and specific details in smaller subsections.
Applications of Sankey Diagrams:
1. Energy Flows: Visualizing the complex web of energy consumption, generation, and transport in energy systems helps stakeholders understand where energy is lost, how different sources contribute, and identify potential optimization areas.
2. Supply Chain Analysis: In supply chain management, Sankey diagrams can illustrate the pathways of goods and services within the supply chain, revealing bottlenecks and identifying opportunities for cost reduction and efficiency improvements.
3. Financial Flows: Sankey diagrams can be used to depict detailed financial transactions within a company or across industries, allowing for analysis of revenues, expenses, and profits.
4. IT System Traffic: In computer networking, Sankey diagrams help track and visualize the flow of data between different devices or processes in an IT system, aiding in identifying performance bottlenecks and optimizing system resources.
Creating Compelling Sankey Diagrams:
1. Data Collection: Accurately measure and gather the flow data for the system you want to visualize. The data typically includes the source, receptor, and flow amount quantified in appropriate units.
2. Select a Tool: Choose a data visualization tool that supports Sankey diagram creation, such as Tableau, Microsoft Power BI, Gephi, or online platforms like Sankeyly.
3. Input Data: Import your collected data into the chosen tool, matching the source, receptor, and flow amount to the corresponding fields.
4. Design the Diagram: Use the graph builder or layout editor of your selected tool to build the Sankey diagram. Experiment with different design options, such as color schemes, sizes, and arrow styles, to enhance readability and visual appeal.
5. Add Labels and Annotations: Clearly label each component in the system, including source, receptor, and the flow amounts, and consider adding annotations for context and data clarification.
6. Review and Modify: Critically review the Sankey diagram for clarity, balance, and consistency. Make adjustments as necessary and ensure that the diagram effectively communicates the intended information.
Limitations of Sankey Diagrams:
While Sankey diagrams offer numerous advantages, they also have limitations to consider:
1. Visual Complexity: Sankey diagrams can become overwhelming if they include too many components and flows, especially when represented in a limited space. Balancing the number of elements to maintain visual clarity is essential.
2. Limited Comparison Capacity: When multiple Sankey diagrams are used to compare different systems, the relative complexity and size differences can prevent easy and accurate comparisons, making simpler visualization methods like bar charts or comparison tables a better choice under such circumstances.
3. Data Density: High data density can lead to clutter, making it difficult to discern specific flows within a complex web of connections.
In conclusion, Sankey diagrams are powerful tools for visualizing the many intricacies of systems where flows, exchanges, and transfers play crucial roles. Their ability to convey complex data in a visually intuitive manner makes them valuable across various industries and applications. By understanding the fundamentals, applications, and limitations of Sankey diagrams, you can harness their full potential to better understand and communicate the dynamics of complex systems.
