Streamlined Streams: The Artful Aesthetic of Sankey Charts Unveiled

Sankey diagrams, often referred to as Sankey charts, are a type of flow diagram used to display the quantities of materials, energy or costs associated with the transfer process. First developed in 1898 by Irish engineer Matthew Sankey to visualize the efficiencies of engineering processes, today Sankey diagrams have become increasingly important in a range of fields, from environmental science to finance to engineering design. This article will delve into the creation and applications of Sankey charts, showcasing their unique artful aesthetic as a powerful tool for data visualization.

Understanding Sankey Charts

Structure and Design

Sankey charts feature a set of arrows, which typically flow from an item’s source to destinations. These arrows have width proportional to the quantity of material, energy, or cost moving through it, making these diagrams both visually engaging and highly informative. The width of these arrows varies in direct accordance with the value it represents, which means they can be used to highlight areas of high and low efficiency or waste.

These directional arrows are connected at junctions referred to as nodes, and the overall flow tends to converge on a particular area or point, such as an end destination or “hot spot.”

The Sankey Principle

Sankey diagrams are based on the Sankey principle of flow, which states that the sum of all energy or materials at each point in the system must balance—essentially, the inflow equals the outflow.

Creating Sankey Charts

Software and Tools

The process of creating a Sankey chart has evolved from complex manual calculations and drafting to the simplicity of using dedicated software and tools. Diverse software solutions such as SigmaPlot, Microsoft Excel with the help of Power Query and Power View, and dedicated platforms like sankeymatic.com or Microsoft Power BI enable the creation of these sophisticated visualizations with ease.

1. Data Preparation: The first step is to gather and organize the data that will eventually be depicted in the chart. This may involve data mining, data cleansing, and data transformation tasks. The data should include the start and end points, and the flows between them.

2. Determining Widths: The width of the stream lines represents the volume of each process or resource flow. It is crucial to ensure that the widths are proportional to the actual volume being transferred. Software often requires a function or equation to map these flows to widths, allowing for accurate representation.

3. Creating the Nodes: Nodes represent the points where there are intersections between the inflows and outflows of processes. The position of these nodes should reflect the logical organization of the processes and flows.

4. Assembling the Chart: Once all the elements are in place, the software assembles the chart, linking the nodes with the stream lines. Formatting tools are used to adjust colors, line styles, and other visual features.

5. Review and Iterate: After creation, the chart needs to be reviewed to see if it communicates the intended message effectively. Adjustments may be necessary to ensure clarity and enhance the aesthetic appeal.

Applications of Sankey Charts

Environmental Science

In environmental studies, Sankey charts are ideal for showcasing the flow of resources like energy through ecosystems or the material flow in production processes. For instance, they could illustrate the flow of waste from production facilities, identifying points of environmental impact.

Energy and Engineering

Energy companies leverage Sankey charts to show the efficiency of power generation, identifying where energy is lost in transmission or transformation processes. They can also be used in engineering design to track the flow of materials or information during the manufacturing of complex systems.

Finance and Economics

For financial analysis, Sankey charts can reveal the flow of funds through an organization or investment portfolio, highlighting areas of profitability and inefficiency. They are useful in illustrating capital and resources moving through financial systems.

Sustainability Reports

Corporate sustainability reports often include Sankey diagrams to communicate how the company is managing resources and minimizing environmental impact.

Data Visualization in Research

Academic research in various disciplines benefits from Sankey charts in illustrating complex processes and data flows. They add clarity to data that might be confusing or obscure in text or traditional graph forms.

Conclusion: Aesthetic and Informative

Sankey charts are a testament to the power of information design, offering an aesthetically pleasing and informative visual representation of the flow of quantities within systems. Their artful aesthetic, characterized by their unique streamline design, makes them indispensable tools for conveying the intricacies of complex data flows. With the right software and thoughtful design, Sankey charts can communicate volumes of information at a glance, making them a staple in data visualization today.

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