Sankey charts are a powerful tool for visualizing flows and data relationships, with applications in fields ranging from engineering to environmental science. Named after its inventor, British engineer Matthew Henry Phineas Riall Sankey (1830–1898), the chart was first used in 1898 to represent energy consumption in the Glasgow shipyard in Fiddler’s Dramatic Magazine. Over the years, the Sankey chart has evolved into a versatile and widely used visualization, offering a clear and intuitive way to communicate complex flow data.

In this article, we will explore the creation and applications of Sankey charts, focusing on their ability to represent flows and provide insights that might be difficult to derive from traditional data visualizations.

Creating Sankey Charts

A Sankey chart is a type of directed graph that assigns width to links, proportional to the flow quantities they represent. Its key components include:

1. Nodes: These represent the entities or categories involved in the flow. In a given diagram, nodes are typically located at the outer edges of the chart as sources and sinks.
2. Links: Also known as flow lines, edges, or arcs in the flow diagram, links represent the relationships between nodes. They can have various shapes, such as arrows or lines, pointing from a source node to a sink node.
3. Flow widths: The magnitude of the flow is visually represented by the width of the links. Wider links indicate a higher flow quantity, while narrower links represent lower flow amounts.

Creating a Sankey chart involves several steps:

• Gather data: Collect the necessary data that describes the flow, including the source, sink, and quantity of each flow.
• Prepare the data: Store the data in a structured format, such as a CSV, with columns for the source, sink, and flow quantities.
• Choose software: There are many tools for creating Sankey charts, such as Tableau, PowerBI, R, Python (with libraries like Sankey and pySankey), and various free online tools. Select one that matches your needs and familiarity.
• Create the chart: Import your data and use the chosen tool to generate the Sankey chart. Design the visualization, choosing colors, labels, and layout options that enhance readability and convey meaning effectively.

Applications of Sankey Charts

Sankey charts are particularly useful in scenarios where the goal is to explain and analyze large volumes of interconnected data flows. Their visual complexity and capacity for storytelling make them suitable for:

1. Energy usage and efficiency: Showing the flow of energy usage and transformations through different systems, such as the breakdown of energy in a power grid or the consumption patterns in industrial complexes.
2. Transportation and logistics: Illustrating the movement of goods or resources through transportation networks, highlighting bottlenecks, optimization opportunities, and distribution trends.
3. Supply chain analysis: Detailing the flow of commodities or information in intricate global supply chains, enabling businesses to identify dependencies and inefficiencies.
4. Environmental flow modeling: Mapping the pathways of water, air, or other natural resources, helping to understand pollution sources, water usage, and the impact of environmental changes.
5. Financial transactions: Visualizing cash flows, transaction networks, or the allocation of investments and profits within industries.

Conclusion

Sankey charts offer a unique approach to visualizing flows, providing clear insights into complex data relationships that might be obscured in lesser visualizations. By creating a chart that emphasizes the importance of flows, their quantities, and the connections between nodes, Sankey charts become powerful tools for decision-making, education, and data analytics. Whether it’s in engineering, environmental science, or business, the ability to explore and understand data through the lens of Sankey charts can uncover valuable insights that drive smarter decisions and strategies.

With the right data preparation and selection of visualization tools, users can leverage the power of Sankey charts to communicate their findings effectively, ensuring that the complex world of flows becomes accessible and understandable to all stakeholders.

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