Sankey charts, also known as Sankey diagrams, are a type of flow chart that visually illustrates how quantities are transferred between systems or entities. They are named after Thomas Sankey, a British engineer who used them in the late 19th century to demonstrate the energy efficiency of his steam engines.
In this article, we will provide a beginner’s guide to creating Sankey charts and explore some of their applications.
1. Basics of Sankey Charts
Sankey charts are particularly useful for representing continuous flow data, like materials, energy, or finances. A flow network that has quantities directed from a source (left) to multiple destination nodes (right) with arrows and thicknesses corresponding to values that flow between nodes is a Sankey digaram.
A Sankey diagram must have the following three main components:
– Node: Represents a category or an entity that flows in and/or out.
– Flow: Represents the transfer of quantity between two nodes, indicated by an arrow and its width.
– Connector: Connects source and destination nodes and shows the flow between them.
2. Creating Sankey Charts
Several tools and programming languages offer functionality for creating Sankey charts:
- Tableau: A popular data visualization tool providing an easy-to-use interface to construct Sankey diagrams based on different data types.
- R (Sankey R): Using the ‘sankeyDiagram’ package, R provides extensive graphical options while allowing for flexible customization.
- Python (Sankey Plot): With ‘NetworkX’ and ‘matplotlib’, Python enables the creation of Sankey diagrams in a code-based approach, providing deep customization.
- D3.js: An advanced JavaScript library for data visualization. D3 offers exceptional control but requires coding proficiency to use.
3. Applications of Sankey Charts
Sankey charts are used in various fields due to their ability to provide a clear visual representation of flow data:
- Energy Audit: Companies use Sankey diagrams to measure energy consumption across production lines by visualizing energy inputs and outputs between processes.
- Material Flow Analysis: Engineers and planners apply Sankey visuals to industrial systems to identify inefficiencies in material usage and optimize resource allocation.
- Marketing Analysis: Businesses track customer routes through different marketing channels by creating Sankey diagrams of audience movement, helping them understand user journey optimization.
- Supply Chain Management: Manufacturers use Sankey charts to show goods movement between locations, identifying bottlenecks in the supply chain process.
- Healthcare: In healthcare systems, providers use Sankey diagrams to visualize patient flow through hospital departments, aiding in resource allocation and improved patient care.
4. Tips for Effective Use
To ensure your Sankey charts effectively communicate your data, consider these guidelines:
- Simplify the Structure: Limit the complexity by keeping the number of nodes and flows to a manageable amount. This helps in maintaining viewer attention and makes the flow easier to follow.
- Ensure Balance: Verify that the flows into a node are equal to those leaving (for a balanced path) or adjust data accordingly if this doesn’t hold true.
- Scale Node Positions: Use a layout that keeps nodes reasonably spaced, preventing overlaps and making label readability easier.
- Color Scheme: Use color to highlight important flows, different categories, or to distinguish trends. A clear legend is essential for understanding the color coding.
- Interactive Elements: Incorporate tooltips or hover effects to reveal detailed data points when users interact with the chart, enhancing the viewer’s understanding.
By following these tips and guidelines, you’ll create insightful and impactful Sankey diagrams to effectively convey the flow of data, resources, or energy within your project or analysis.
Conclusion
Sankey charts offer a visually appealing and informative way to showcase flow data, making them valuable tools in various sectors, including engineering, healthcare, energy, and more. Whether you’re new to data visualization or an experienced professional, understanding the basics of Sankey charts and applying your knowledge effectively will help you create compelling diagrams that communicate essential insights effortlessly.
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