Sankey diagrams are a remarkable visualization tool, which elegantly capture the flow of materials, energy, and momentum in complex systems. Their distinctive design allows for an intuitive understanding of the quantity and efficiency of processes. With their ability to highlight areas of opportunity and inefficiency, they have become popular in logistics, manufacturing, environmental science, and other fields where the flow of materials must be carefully monitored. Here, we delve into the art of interpreting and creating Sankey diagrams for material analysis to help you master this powerful method of data visualization.
### Understanding Sankey Diagrams
A Sankey diagram is characterized by arrows that depict the flow of material, energy, or information from one process to another. The width of the arrows represents the rate or quantity of flow. The diagram’s width generally decreases when a flow is split into several branches and increases when arrows merge, accurately reflecting the distribution of materials or energy through the system.
### Interpreting Sankey Diagrams
Interpreting a Sankey diagram begins by identifying the main stages of the flow process. Here’s how to do it:
**1. The Channels**: As the main conduit for material flow, channels are the horizontal segments along the Sankey diagram. They represent processes, and their length is indicative of the flow volume related to each process.
**2. The Arrows**: The width of the arrows represents the relative quantity of material or energy being transmitted along each path.
**3. The Nodes**: These are the points where arrows begin or end, representing processes.
**4. The Direction of Flow**: The direction is usually consistent, from left to right, which conveys the flow of time or a process sequence from beginning to end.
**5. Key Indicators**: Look for areas where the arrows narrow or widen, which could indicate inefficient areas or bottlenecks.
To gain deeper insights:
**1. Summation of Arrows**: When the end of one arrow merges with the beginning of another, the combined arrow should be wide enough to represent the total of the flows from both arrows.
**2. Efficiency Analysis**: Areas where the width of arteries narrows represent where material is spent or lost.
**3. Process Comparison**: Diagrams with arrows of the same width at a certain stage show equal rates of flow for different processes.
### Creating Sankey Diagrams for Material Analysis
Crafting a Sankey diagram involves careful calculation of the flow rates and some design choices. Here’s a step-by-step guide:
**1. Define the Processes**: List the processes that involve material flow within the system under analysis.
**2. Identify Flow Quantities**: Gather the flow rates for these processes in units relevant to your data, such as mass or volume.
**3. Normalize the Data**: Since Sankey diagrams often display multiple flows on a single chart, it’s essential to relate flow rates to a common denominator.
**4. Set Up the Diagram**: Start your diagram with an entry point representing the start of the flow, followed by the principal pathways along which the flow moves.
**5. Assign Arrows**: Make each arrow represent the flow from its source process to its subsequent process. Label the arrows with the material flow values.
**6. Design the Diagram**: Use software or drawing tools designed for Sankey diagrams (like SankeyFlow, yEd, or other specialized software) for accurate visualization. Software provides better control of the widths of the arrows to match your data precisely.
**7. Validate the Diagram**: Ensure that the flow into each node equals the flow out from that node to maintain balance in your diagram.
**8. Review and Iterate**: Present your Sankey diagram, review feedback, and make adjustments as necessary.
**9. Finalize the Presentation**: Once you have a balanced and informative diagram, consider how to make it the most effective visual communication tool. Use clear labels, color coding, and a consistent arrow direction.
In conclusion, Sankey diagrams are a useful tool for material analysis due to their ability to represent complex flow systems with simplicity. By accurately interpreting and meticulously crafting these diagrams, you can unlock powerful insights for better decision-making, process optimization, and understanding of material flows in any system.
