Sankey charts, named after their inventor, Scottish engineer and physicist Matthew Henry Phineas Riall Sankey, are a type of flow diagram that allows you to visualize the distribution, flow, and conservation of a quantity, such as energy or material, through a series of interconnected nodes or elements. These charts are particularly advantageous for illustrating complex data flows and identifying patterns and relationships between different components.
In this article, we’ll explore Sankey chart creation and applications, offering a step-by-step guide to mastering this powerful data visualization tool and its varied uses in various fields, including energy consumption, economics, and environmental studies.

1. Understanding Sankey Charts

Sankey charts display flows between different entities, using rectangles for nodes and links for the flows. The width of the links indicates the volume or magnitude of the flow, making it easy to identify relationships and connections at a glance. This feature is particularly useful for visualizing large datasets that might be otherwise difficult to comprehend.

2. Key Components of a Sankey Chart

• Nodes: These represent entities, such as sources and targets. Nodes can be custom labeled to provide context for each endpoint.
• Links: Also known as edges, these lines connect nodes and denote the flow between them. The thickness of a link indicates the magnitude of the flow.
• Balances: These are annotations showing the net flow at each node, helping to verify the conservation principle across the entire chart.

3. Steps to Create a Sankey Chart

Step 1: Data Preparation

Before you start creating a Sankey chart, ensure your data is organized with columns for:
– Source: The entity that initiates the flow.
– Sink: The entity that receives the flow.
– Flow: The magnitude of the flow between the source and sink.
– Node labels: Names that will be displayed on the nodes. You can also include descriptions in the tooltips.

Step 2: Select a Visualization Tool

Choose a visualization tool or software that supports Sankey charts, such as:
– Tableau
– Plotly
– D3.js
– Microsoft Power BI
– Google Charts

Step 3: Loading Data

Import your data into the chosen tool. Most tools offer an option for direct data connection or CSV file uploads.

Step 4: Building the Chart

• Define the axes: Typically, nodes are placed along axes.
• Plot the flows: Insert a Sankey chart type, input your data, and map nodes and flows accordingly.
• Adjust settings: Customize colors, labels, and tooltips for a better user experience. Ensure the chart is clear and not overcrowded with too many nodes or flows.

Step 5: Review and Finalize

• Check for accuracy: Verify that the flows and balances match your data and the principles of flow conservation.
• Aesthetic adjustments: Optimize the visual layout and color schemes for better readability and aesthetic appeal.
• Interactive elements: If using a more advanced tool, consider adding interactive features such as hover effects or filtering options.

4. Applications of Sankey Charts

• Energy Consumption: Analyze energy flows in buildings, utilities, or industries, highlighting sources, transformations, and usage patterns.
• Economic Models: Visualize trade relations, expenditure flows, or sectoral compositions in an economy.
• Environmental Studies: Track material or pollution flows through ecosystems, industries, or global supply chains.
• Social Network Analysis: Represent the flow of information, connections, or interactions within networks.

5. Conclusion

Sankey charts are an invaluable tool for visualizing complex flows and distributions in a comprehensible and engaging way. By following the steps outlined above, you can create impactful Sankey diagrams tailored to your specific data and visualization needs. Whether applied in energy conservation studies, economics, or environmental research, these charts provide a powerful means to communicate insights and patterns clearly.

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