Decoding the Complexity: A Comprehensive Guide to Creating and Interpreting Sankey Diagrams
Sankey diagrams were first invented in the 19th century by Scottish engineer and statistician William John Macquorn Rankine. Initially, he designed them mainly for power flow analysis. Today, this graphical representation is widely used across several disciplines, including economics, business, environmental science, power engineering, etc.
A Sankey diagram is a special kind of flow diagram developed to represent flows. They are most often used to illustrate material, energy, or other quantity flows in a system. The width of each flow line in the diagram represents the quantity of that flow, allowing viewers to quickly visualize the relative importance of different flows.
Creating a Sankey Diagram
Here are the steps to create a Sankey diagram:
1. **Gather Data**: Before creating your diagram, it is essential to collect accurate data. This data typically includes the source and destination of different flows, and the quantities being transferred in each direction.
2. **Choose Your Diagramming Tool**: There are several software tools and online platforms designed for creating Sankey diagrams, such as Microsoft Excel, R (with packages like ‘networkD3’), Python (using libraries such as ‘Sankey’), Tableau, and ConceptDraw PRO.
3. **Prepare Your Data for Visualization**: In your chosen tool, arrange your data in rows or columns, ensuring there’s a column for origin, another for destination and a third for the value of flow. This data structure will help your tool create the flow lines accurately.
4. **Use Software Tools to Map the Flows**: Every software has unique features and specific methods for visualizing Sankey diagrams. Using the data prepared in the previous steps, you can input the source and destination nodes into your software to create the flow lines. Adjusting the width of the lines according to the magnitude of the quantity flows is a crucial step in ensuring accuracy and readability of your diagram.
5. **Customize Your Diagram**: Once your diagram is laid out, you can customize its appearance. This includes changing the colors of nodes and lines, adding labels to nodes and arrows, and adjusting the layout, flow direction, or animation settings according to your specific requirements.
Interpreting a Sankey Diagram
Interpreting a Sankey diagram requires careful scrutiny, as these diagrams can be complex with numerous flows to consider. Here are key steps to maximize your understanding:
1. **Identify Nodes (Sources and Destinations)**: The nodes in a Sankey diagram are points where flow begins or ends. These are usually presented at the top and bottom of the diagram, signifying the start and end destinations of your flows. Nodes are especially important in identifying what’s entering and leaving a process or system.
2. **Analyze the Flow Lines**: The main elements are the flow lines representing the movement of quantities from one node to the next. The width and color of these lines provide visual insights into the volume of flows and their relative proportions. For instance, a thicker, predominantly red flow line might indicate a high volume of product or energy being imported from a specific location or source.
3. **Examine Transfers Between Different Levels**: In a three-dimensional Sankey diagram, flows can be shown between different levels, forming a hierarchical structure. Pay attention to how these flows are distributed across levels to understand complex systems’ interactions and dependencies.
4. **Utilize Legends for Color and Size**: Sankey diagrams often include a color-coded legend. This helps explain the color scheme in terms of the data they represent. Size can be color-coded to signify the volume of the flow. This can allow the viewer to quickly discern which flows are more significant.
5. **Look for Patterns and Trends**: By analyzing the entire structure of the Sankey diagram, look for any patterns that might indicate a regular sequence of flows, preferred directions, or cycles. These patterns can offer valuable insights into system behavior and performance.
Conclusion
In conclusion, creating and interpreting Sankey diagrams effectively involves comprehensive data organization, the right software tools, and an insightful understanding of graphical representation techniques. By applying the steps outlined above, individuals from diverse fields can visualize complex data flows succinctly, facilitating communication, understanding, and decision-making.
Whether you’re analyzing traffic data, flow dynamics in ecosystems, or material distribution in industrial processes, Sankey diagrams serve as invaluable visual aids for comprehending intricate relationships and flows within complex systems.
