Sankey charts, also known as Sankey diagrams, are a type of flow visualization that are used to represent the different flows and connections within a system. These charts are named after Captain Matthew Henry Phineas Riall Sankey, a civil engineer who first used the diagram in the 1850s to illustrate the energy transformations within a steam engine.
In this comprehensive guide, we will explore the power of Sankey charts in unlocking insights by visualizing flows and connections. From their basic principles and construction to their advanced uses, this guide will provide you with a thorough understanding of how to leverage Sankey diagrams as a data visualization tool for any system you analyze.
### 1. **Understanding Sankey Diagrams**
Sankey diagrams display flows as arrows with widths proportional to the flow quantities. Each node represents an entity (source, sink, or transformer) and the flow between nodes illustrates transactions, flows, or movements from one to another.
### 2. **Components of a Sankey Diagram**
– **Nodes**: These represent entities within the system. Depending on the visualization, nodes can be categorized into “sources”, “sinks”, or “transformers”.
– **Links**: These are the arrows connecting nodes, where the width of the link is proportional to the flow or quantity.
– **Labels**: Both node and link labels provide context, usually indicating the nature or description of the entities and flows.
– **Colors**: Colors are often used to categorize or differentiate between different types of flows, adding another layer of information to the diagram.
### 3. **Constructing Sankey Diagrams**
– **Data Collection**: Gather data on the entities within your system and the flows between them. Ensure the data is structured in a way that can be easily mapped to nodes and links.
– **Choosing Tool**: Select a data visualization tool that supports the creation of Sankey diagrams, such as Tableau, Power BI, or Python libraries like Plotly and Graph-tool.
– **Layout and Design**: Arrange nodes and links in a way that visually highlights connections and prevents visual clutter. Tools often have default layouts, but manual adjustment can be useful for complex data sets.
– **Interactivity**: Adding interactive features, such as tooltips, animations, and filters, can enhance the user experience and make the diagram more informative.
### 4. **Advanced Uses of Sankey Diagrams**
– **Multi-Level Diagrams**: For complex systems with multiple inter-connected flows, consider breaking down the flows into sub-flows using different sets of categories or sub-nodes.
– **Overlays**: Layering additional data, such as time series or quantitative data on top of the Sankey diagram, can provide deeper insights into how flows change over time or under different conditions.
– **Color Coding**: Advanced applications might involve using color schemes to encode additional variables, such as cost, profit, or environmental impact of each flow.
### 5. **Case Studies**
Exploring real-world examples can provide invaluable insights into how Sankey diagrams are used effectively:
– **Energy Usage**: Visualizing energy flows from different sources to consumption points, where the width of the link represents the amount of energy used.
– **Supply Chain Analysis**: Tracking the flow of goods from suppliers to manufacturers and consumers, highlighting bottlenecks and opportunities for optimization.
– **Transportation Networks**: Analyzing traffic flows between different points in a network to understand congestion and optimize routes.
### 6. **Best Practices**
– **Clarity and Simplicity**: Avoid overcrowding the diagram with too many flows and too many labels. Simplifying the layout makes it easier to understand at a glance.
– **Consistency**: Use consistent colors and symbols to maintain clarity and ease of interpretation.
– **Interactive Elements**: Keep the interaction of the chart intuitive so that viewers can quickly explore the details of each flow.
### Conclusion
Sankey charts are a powerful tool in the data visualization arsenal, especially when it comes to illustrating the movement, transformation, and distribution of entities within a system. By leveraging the right tools, techniques, and best practices, you can unlock deeper insights and make your data more accessible and engaging to your audience. As you explore incorporating Sankey diagrams into your analysis or presentations, consider the unique characteristics of your data and the story you wish to tell, letting the diagrams guide your decision on complexity, layout, and interactivity.
