Introducing Sankey Charts: A Visual Powerhouse for Data Stories
For those new to the world of data visualization, the concept of a Sankey chart can seem intimidating at first. However, with their distinctive, flowing streams and precise graphical representation of the transfer of energy, materials, or costs, Sankey diagrams are a versatile tool for illustrating the flow of various entities through a process. The beauty of Sankey charts lies in their ability to concisely convey the relationships and proportions of energy or information flow.
In this beginner’s guide, we’ll dive into the essence of Sankey charts, walk you through their components, and show you how to create an effective Sankey chart that will help bring your data to life.
Understanding the Basics
What is a Sankey Chart?
A Sankey chart is a type of directional flow diagram, which was introduced by 19th-century engineer and statistician, Karl Sankey. Sankeys are best suited for representing the flow of something over time or between different components in a process. They are particularly useful for showing the efficiency of a process, where losses or inefficiencies are easily identifiable.
Why Use a Sankey Chart?
1. Visually demonstrate the dynamics of a system’s components
2. Highlight inefficiencies, bottlenecks, or areas for improvement
3. Compare the sizes of flows side-by-side
4. Present complex information in a simple, intuitive format
Components of a Sankey Chart
1. Flow Lines: Represent the quantity flowing through a system. Widths vary according to the amount of flow.
2. Nodes: The points where flow lines originate or terminate, indicating a component of the system.
3. Direction: The orientation of the flow lines, typically from left to right or top to bottom, suggests the progression of the process.
4. Arrows: Often used to show the direction of the flow.
5. Labels: Identify the components and flows within the chart.
Creating Your Sankey Chart
1. Identify the purpose and scope of your chart. What process or flow are you trying to represent?
2. Define the components and the flow lines that illustrate the transitions between these components.
3. Assign the quantity of each flow, either as absolute values or relative to the total flow.
4. Choose the appropriate direction for your flow lines.
5. Use visualization software or libraries, such as D3.js, Power BI, or Python’s Sankey Library to create your chart.
6. Customize the appearance to align with your preferences and the data’s story.
Common Uses of Sankey Charts
1. Energy Systems: Show energy flow through power plants or the carbon emissions of a country.
2. Production Lines: Visualize the flow of materials through different stages of production.
3. Logistics: Track the movement of goods through various transportation routes.
4. Environmental Studies: Illustrate the carbon footprint or water flow in a given process.
5. Finance: Display the flow of funds within an organization or project.
Remember, as you embark on your Sankey chart creating journey, practice is key, and the more Sankeys you produce, the better you’ll understand the nuances of this powerful visual tool. With these guidelines and a bit of practice, you’ll soon become a seasoned pro at crafting compelling and informative Sankey diagrams.
