Sankey charts are a visualization tool that represent flows between different categories or nodes. The width of the lines between the categories is proportional to the flow volume, making it easy to see which flows are the most significant in a system. This article will explore the power of Sankey charts, their creation, and some of the ways they can be used to visualize data in a unique, intuitive way.
What are Sankey charts?
Sankey charts are named after Captain John H. Sankey, who first introduced them in the late 19th century to illustrate the flow of steam through a factory. These charts represent data as a series of arrows or lines, where the thickness of the line corresponds to the volume of the flow. In a Sankey chart, nodes represent categories, and flows represent the movement of data between those categories.
Key features of Sankey charts
- Flow Volume Representation: The width of the lines is proportional to the amount of flow between nodes, making it easy to compare volumes.
- Flow Direction: Sankey charts can show the direction of flows, indicating the direction of data movement.
- Compactness: They are designed to be compact, making it easier to compare multiple flows within the same chart.
- Customizability: Sankey charts can be customized in various ways to emphasize specific flows or make the chart more visually appealing.
Applications of Sankey charts
Energy systems
One of the most common uses of Sankey charts is to visualize energy systems, showing how energy moves through different stages of production, transmission, and consumption. This helps in identifying inefficiencies, areas for improvement, and potential areas for energy conservation.
Supply chains
Sankey charts are ideal for representing supply chain flows. They can illustrate the movement of goods, material, or information between suppliers, manufacturers, distributors, and retailers, highlighting the most critical routes or bottlenecks.
Traffic networks
In transportation planning, Sankey charts can display traffic flows between different locations, airports, or road networks. This helps in understanding congestion patterns, identifying high-traffic routes, and optimizing traffic management systems.
Data and information flows
Sankey charts are useful for visualizing the flow of data within an organization, showing which departments or systems receive or send the most data. This can aid in enhancing data management and improving data access and tracking.
Creating Sankey charts
Creating a Sankey chart requires data about the flow volume and the connections between nodes. Here’s a basic guide to creating a Sankey chart using popular data visualization tools like Tableau, Microsoft Power BI, or even basic software using raw data tables:
- Data preparation: Prepare your data with columns for source, target, and flow volume.
- Choose the tool: You can use software tools like Tableau, Power BI, or create one using libraries like matplotlib or Plotly in Python.
- Data loading: Import the data into your tool of choice. In some tools, you might need to use a specific table structure or import the data as CSV.
- Map data to visualization: Assign the source and target nodes, and the flow volume to the chart. Make sure your data is sorted and organized correctly.
- Create the chart: Use the visualization tool’s features to create a Sankey chart. Adjust the title, colors, and labels according to your preference.
- Enhance the visualization: Add additional features like tooltips, legends, or background images to make the chart more informative and appealing.
Example: Sankey chart in Tableau
- Load your data into Tableau.
- Drag the “Source category” to the Columns shelf, “Target category” to the Rows shelf, and “Flow volume” to the Size card under Marks.
- Change the marks type to “Link” to create Sankey connections.
- Adjust the “Source Category” and “Target Category” marks to enable tooltips for displaying flow volumes.
- Customize colors, tooltips, and chart layout as required.
Conclusion
Sankey charts are a powerful tool for visualizing and understanding complex flows of data, energy, information, or traffic. Their ability to convey flow volumes and provide insights into the efficiency and distribution of resources make them invaluable in various fields, from energy management to supply chain optimization. By leveraging the customization options available in modern data visualization tools, anyone can create compelling Sankey charts tailored to their specific needs, making them a versatile addition to any data analysis toolkit.
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