The River of Data: A Sankey Surge in Visual Storytelling

In the vast ocean of data visualization techniques, the Sankey diagram stands out as a rare gem with a unique ability to depict complex processes with simplicity and elegance. Similar to a river flowing through landscapes, the Sankey chart represents the flow of data, energy, or resources between different elements in a system, where the thickness of the arrows represents the volume of the flow. This article will delve into the mechanics of creating Sankey charts and explore their applications across various industries.

What is a Sankey Diagram?

A Sankey diagram is a type of flow diagram that shows the quantity of flow through a process, where the width of the paths of flow is proportional to the quantity of flow. They are essentially a graphical tool to represent the magnitude of material, energy, or cost flows into, out of, and within an energy, material, or cost system at various stages.

Initially developed by William Playfair in the 19th Century and refined into the modern form by Max Schmid in the 1920s, Sankey diagrams are a descendant of flow charts and process maps but with a distinct visual language tailored to the depiction of flows.

The Mechanics of Creating Sankey Charts

Software Tools

Creating a Sankey chart can range from pen and paper sketches to sophisticated software tools such as:

• Microsoft Excel
• Adobe Illustrator
• OpenRefine
• Tableau
• R programming language with packages like ‘streamplot’ or ‘ggsankey’

Here’s a quick step-by-step guide to creating one using Excel:

1. Organize Your Data: Gather your input and output data for the various processes or components you want to visualize.
2. Set Up Your Structure: Create a structure with two sections for flows; one for the inputs and one for the outputs.
3. Draw Arrows: Using the data from your structure, draw arrows to represent the flow of information or resources from the inputs to the outputs.
4. Adjust Flow Width: Make the arrow wider as the flow increases.
5. Label and Title: Add clear, concise labels for each section and an informative title.

Best Practices

• Keep it Simple: Sankey diagrams can seem complex. It’s best to keep each chart focused on a single process or set of processes to avoid clutter.
• Select the Right Scale: Choose a scale that accurately represents the relative flows but does not overcomplicate the visual.
• Use Color Consistently: Applying a coherent color scheme enhances readability and helps to identify connections and patterns.

Applications of Sankey Diagrams

Sankey diagrams are versatile and popular for a variety of applications, especially where illustrating flow and connectivity is crucial:

Energy and Environmental Studies

These diagrams can chart all energy uses and losses during manufacturing processes or building construction. They are invaluable for demonstrating potential improvements in energy efficiency, highlighting where resources are being wasted or underutilized.

Financial Analytics

In the financial sector, Sankey diagrams can track the flow of funds, revealing where and how capital is allocated and spent, making it a useful tool for budgeting and investment management.

Urban Planning

Urban planners can use Sankey diagrams to map the movement of traffic through a city, visualizing commuting patterns, road utilizations, and public transit flows to design more efficient systems.

Supply Chain Management

Sankeys help break down complex supply chains, illustrating the flow of materials, energy, or information from suppliers to customers, which can be critical for identifying bottlenecks or inefficiencies.

Software Engineering

Developers can use Sankey diagrams to visualize the flow of data or processes within software, assisting in understanding system design, performance bottlenecks, and resource allocations.

Agriculture and Food Chain

Sankey diagrams can provide insights into food systems, illustrating the energy and resources used up to and including food manufacturing, processing, and delivery.

Conclusion

Sankey diagrams have emerged as an indispensable tool for visual storytelling, offering an intuitive way to depict and understand complex data flows. While their creation might seem intricate at first, with the right software and data organization, Sankey diagrams can be a straightforward and effective means of communicating the essence of flow data. As our data-driven culture continues to thrive, Sankey diagrams will undoubtedly play an increasingly central role in how we understand and visualize the information landscapes around us.

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