Decoding Complexity with Sankey Diagrams: A Comprehensive Guide to Visualizing Flow and Material/Cost Distribution
Sankey diagrams are a powerful visual tool that enable complex systems to be comprehensibly understood. This article examines the nuances, benefits and limitations of Sankey diagrams, as well as offering a guide on how to effectively create and interpret them.
Overview of Sankey Diagrams
Sankey flow diagrams illustrate not just the quantity of flow, but also the direction. They were first developed in the United States in the 1850s for energy balance studies, but have since been applied in numerous fields for better visualization of flow networks.
Structure and Components
In a Sankey diagram, two main components are observed: entities and connections. Entities are the starting and ending points, like sources, sinks and transformations. Connections or ‘arrows’ show the flow between these elements, representing material, energy, cash, etc.
Coloring and widths encode important data – the width of the arrow represents the magnitude of the flow, usually defined by the weight (mass, volume, electricity etc) being transported between entities. Color codes help distinguish different types of flows like energy consumption by different sectors.
Benefits of Sankey Diagrams
1. Enhanced comprehension: Sankey diagrams are particularly powerful in depicting complex systems. By visually representing quantities and directions, they simplify sophisticated processes into easily digestible, understandable illustrations.
2. Communication: These diagrams are beneficial for sharing intricate information with stakeholders who might find raw data unintelligible. They are an effective tool for communicating changes, advancements, and dependencies within a system.
3. Comparative analysis: By allowing the user to compare the magnitude of flows across a single dataset, Sankey diagrams facilitate deeper insights into the systems they represent.
Creating a Sankey Diagram
Selecting Software: Tools such as Gephi, Nodebox, Tableau, and Microsoft Excel can all be used to construct Sankey diagrams. Gephi is a dynamic tool for complex networks, Nodebox is great for Python users, Tableau is easy to use with a wide range of dataset compatibility, and Excel offers a simple approach for those who are familiar with the spreadsheet.
Constructing Data: Your dataset should include entities and their connections over time, the quantity or attribute of the flow between each pair of entities, and any other necessary variables. Once this information is collected, your data can be inputted into your chosen software.
Layout and Design: Sankey diagram design is not just about data input. Ensure your diagram isn’t overcrowded – too many arrows can lead to confusion. Use groupings and coloring strategically to guide the viewer’s eyes effectively.
Limitations
Sankey diagrams, however, have their limitations. Firstly, they may not be suitable for very large or detailed datasets due to the complexity and potential for clutter. Secondly, the width of arrows can sometimes be misleading, particularly if there’s no explicit scale.
Additionally, Sankey diagrams are effective for steady-state systems but may not fully represent real-time or time-varying data. Lastly, they can sometimes fail to convey the direction of flow if not carefully labeled, which can cause misinterpretation.
Conclusion
Sankey diagrams are powerful tools for data representation that effectively reveal underlying relationships within complex systems in a simple and visually intuitive manner. Whether visualizing financial flows, energy systems, or material distribution, these diagrams offer a compelling way to simplify and provide unique perspectives on complex data patterns. Yet, as with any graphical representation, careful consideration should be given to the context and the nature of the data being presented.
In essence, Sankey diagrams hold great promise for enhancing both the comprehensibility and persuasiveness of data interpretation. Whether a business leader seeking to understand the impact of different revenue streams on financial health, an environmental scientist trying to explain energy usage patterns, or a designer aiming to highlight resource conservation, Sankey diagrams offer a novel and accessible way to visualise and communicate flow dynamics within their respective systems.
