Sankey charts, also known as Sankey diagrams, are a type of flow diagram that illustrate the movement of material, energy, or cost through a process. Named after their inventor, German engineer and engineer Johann Heinrich Mantel, these charts provide an excellent way to summarize and visualize large datasets, making them a powerful tool for understanding complex systems and the relationships among different processes involved. Here, we take an introductory look at what Sankey charts are, how they’re constructed, and why they’re beneficial for data visualization.
### Understanding the Basics
At their core, Sankey charts convey how energy, material, or money flow through a system. Each element or process is represented by an arrow, with the width of the arrow indicating the quantity of the substance or energy being transferred. The sum of all arrow widths at each stage should add up to the total input or output of the system.
### Constructing a Sankey Chart
Creating a Sankey chart involves several steps:
1. **Data Collection**: Gather data on the entire system you wish to analyze. This could include the amount of energy consumed, the materials used, or the financial inflow and outflow in a business process.
2. **Identify Processes**: Break down the data into processes or systems. For example, in a manufacturing process, you might separate out stages such as raw materials, production, and transportation.
3. **Determine Direction and Flow**: Determine the direction of the flow within each process and between processes.
4. **Calculate the Flow Widths**: Evaluate the amount of substance or energy flows through each process. The wider the arrow, the more substantial the flow.
5. **Apply Sankey Algorithms**: Use Sankey chart software or tools that automatically allocate flows to the widths of the arrows, ensuring that the sum of flows at each node equals the sum of incoming and outgoing flows.
### Visualizing in Practice
Sankey charts are particularly useful in various fields, such as:
– **Energy Efficiency**: To illustrate how energy is lost or wasted in various systems.
– **Logistics**: Tracking the flow of goods and services within a supply chain.
– **Financial Reporting**: Showcasing the flow of money through a company or an economy.
– **Environmental Analysis**: Demonstrating the pathways of water cycles and material flows.
#### How to Read a Sankey Chart
When interpreting a Sankey chart, identify the main processes, nodes (points where arrows meet), and the direction of flow. Look at the widths of the arrows and note any bottlenecks—where a flow width is unusually small relative to other flows in similar conditions.
### Crafting the Message
Sankey charts are versatile but can be read with care. They are particularly valuable for presenting data in a storytelling format, guiding viewers through processes and highlighting important aspects of the information they convey.
### Getting Started
If you are new to using Sankey charts, here’s a brief list of resources to get you started:
– **Sankey Diagram Tool**: An online Sankey diagram tool that makes it simple to create your own diagrams.
– **Sankey Diagrams by Mark Newman**: An academic site where you can find tutorials and detailed discussions of Sankey diagrams.
– **Books**: “Sankey Diagrams: Designing the Visual Language of Flow” by Prof. David McCandless and “Analytical Network Principles and Applications with SANKEY Diagrams” by Dr. Egon Bekkenkamp.
In conclusion, Sankey charts are an effective way to convey complex data flows in a manner that is more intuitive and engaging than traditional charts. By understanding and utilizing the power of Sankey diagrams, you can provide insights into your data that are both captivating and informative. Start by exploring the tools available and experimenting with different data to find the best way to express the narrative of your data flows.
