Sankey charts are a visual representation of flows and materials moving between different points in a system. They are popular in several industry verticals because they provide a clear visualization of the data flow and relationships between different entities. By visualizing flows with a Sankey chart, we can easily discover insights, patterns, and trends that may not be apparent from tabular data alone.

In this article, you will learn about the creation and applications of Sankey charts. We will cover the basic concepts, tools, and techniques needed to create Sankey diagrams, and explore common use cases where they can enhance data narratives. Let’s dive in.

Basic Concepts of Sankey Charts

Overview: Before we delve into the creation of Sankey charts, it’s important to understand the key elements that make up a Sankey diagram.

1. Nodes: These are rectangles that represent individual components or entities in the system you are analyzing. For instance, you might represent different departments or categories of information.
2. Links: These are bent lines connecting the nodes, representing the flows between the entities. The width of the links corresponds to the magnitude of the flow, typically scaled to the area. Larger flows are represented by thicker lines, while smaller flows by thinner ones.
3. Bars: Sankey charts often display bars parallel to the link lines, which can help in visualizing the flow rates more clearly.

Creating a Sankey Chart

Step 1: Define Your Data

The first step in creating a Sankey chart is to structure your data appropriately. Each flow needs a source, a target, and a value (like number of units, dollars, or another metric). Your data should be organized in a format where each row represents one flow from the source to the target.

Step 2: Choose a Tool

There are several tools available for creating Sankey charts, ranging from simple online options to more complex software packages that support data-driven designs. Below, we’ll outline the process using two popular tools: Tableau and Python (using the networkx and matplotlib libraries for a more customizable approach).

Using Tableau

1. Upload your data to Tableau.
2. Connect the source and target fields with the flow value field.
3. Drag fields to the appropriate parts of the visualization pane (dimensions on the columns shelf, measures on the rows shelf, and table calculations if needed).
4. Choose the Sankey chart type from the toolbar.

Using Python (networkx and matplotlib)

1. Install the required libraries: networkx, matplotlib, and scipy (optional).
2. Load your data into a pandas DataFrame.
3. Create a Sankey graph using networkx and draw the graph with matplotlib.

Step 3: Adjust and Enhance the Sankey Chart

Once the basic chart is in place, adjust aesthetics like colors, font sizes, and link widths as needed. Consider using different colors to highlight specific flows or categories.

Applications of Sankey Charts

Energy Systems

In the energy sector, Sankey charts are used to visualize the energy flows from different sources, through transmission networks, and to different end-use sectors or locations. This helps in identifying energy losses, determining the efficiency of energy conversion, and planning for renewable energy integration.

Supply Chain Analysis

For businesses, Sankey charts offer a way to visualize the inventory and flow of products or components through various stages of the supply chain, like raw materials suppliers, manufacturers, distributors, and retailers.

Social Media Analysis

In digital platforms, Sankey charts can summarize the flow of users visiting different pages from various sources, helping to optimize UX and content strategies by identifying popular paths and bottlenecks.

Environmental Impact Assessment

Sankey diagrams can be instrumental in illustrating the material flow analysis in industrial facilities, showing consumption, production, and waste generation. This aids in understanding and minimizing environmental impacts.

Conclusion

Sankey charts are a powerful tool for visualizing complex flow data. By following the outlined steps and techniques, you can create effective Sankey diagrams tailored to your specific needs. Whether you’re presenting insights in an annual report, conducting a supply chain audit, or analyzing traffic patterns on a digital platform, Sankey charts can help you tell a comprehensive story with your data. With practice and a deeper exploration of these tools, you’ll find even more innovative applications for visualizing your data’s flows and enhancing data narratives.

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