Sankey charts, a type of flow diagram, are a fascinating way to visualize the flow of data or quantities between different categories or nodes. They are named after the Reverend Hugh M. Sankey, a leading steam engine designer born in 1803 in Scotland, and are often employed to showcase energy consumption, process improvements, or supply chains. This article will guide you on how to create and utilize Sankey charts for various applications.

How Sankey Diagrams Function

Sankey diagrams are characterized by arrows or lines, each representing a quantity of flow, which visually connects the nodes that constitute the system being analyzed. Each arrow at a source node extends to a node at its destination, with the width of the arrow representing the volume of flow. This graphical representation allows for a quick understanding of the source and the destinations of the flows, as well as the volume associated with each.

Key Elements:

1. Nodes: These are the points where the flows originate or terminate in the system. In a Sankey diagram, each node is clearly labeled with a name and often, a percentage of the total flow to differentiate them at a glance.

2. Arrows/Links: These represent the flow between nodes. The width of the arrows signifies the volume of the flow. In essence, a wider arrow conveys a larger amount of data or quantity being transferred, while a thinner arrow indicates a smaller volume.

Creation of Sankey Diagrams

To create a Sankey chart, you will need data that defines the sources and destinations along with the flow quantity between them. Here’s a simplified guide to creating a Sankey chart using popular tools:

Tools and Software

• Microsoft Power BI: A powerful data analysis and reporting tool.
• Tableau: A leading data visualization tool.
• D3.js: A JavaScript library for producing dynamic, interactive data visualizations in web browsers.
• Vizzlo: An online platform with templates for various charts and diagrams.

Step-by-Step Guide:

1. Prepare Your Data: Your dataset should include columns that define the ‘source’, ‘destination’, and ‘value’. The ‘source’ and ‘destination’ should label the nodes, and ‘value’ indicates the flow quantity between them.

2. Data Import: Import your data into your chosen tool.

3. Chart Creation:

   • In Power BI and Tableau, you can select the Sankey diagram template from the list of visualizations. Drag and drop your columns into the respective fields.
   • D3.js requires coding to create a custom Sankey diagram, involving loops and data manipulation in JavaScript.
   • Vizzlo allows you to choose among pre-designed templates, requiring you to input your column data.

4. Customize Your Diagram:

   • Adjust the visualization style, such as arrow colors, node shapes, and font styles.
   • Optimize the layout of nodes and arrows for easier interpretation.

5. Review and Publish: Review your chart for clarity and accuracy, then publish it within your report or dashboard.

Applications of Sankey Diagrams

1. Economic Analysis

Use Sankey diagrams to analyze the flow of trade between countries, understanding where a country’s imports and exports originate and end.

2. Sustainability Monitoring

Visualize the energy consumption or greenhouse gas emissions flows through energy producing processes in factories, homes, or industries. This helps pinpoint which areas have the highest impact and can be targeted for efficiency improvements.

3. Process Improvement

Map out manufacturing processes, showing which inputs and outputs lead to higher inefficiencies, guiding strategies for optimization and waste reduction.

4. Marketing Analysis

Track the journey of customers from the point of awareness to conversion, identifying the most effective marketing strategies and optimizing ad spending.

5. Traffic Analysis

Analyze the patterns of traffic flow within a city, understanding the movement of individuals or vehicles between different destinations during peak hours.

6. Biological Networks

Visualize metabolic pathways, showing the flow of molecules between reactions, or protein-protein interactions, aiding in the study of biological systems and disease mechanisms.

7. Social Network Analysis

Chart relationships between individuals or entities in social networks, mapping the connections, influence, and information flow within the network.

Conclusion

Sankey diagrams are an incredibly versatile tool for visualizing flows and connections in a variety of contexts. By accurately representing the volume, source, and destinations of flows, these diagrams enable stakeholders to make informed decisions, optimize processes, and communicate insights clearly. Whether you’re analyzing data for business strategy, understanding energy usage patterns, or exploring biological pathways, Sankey charts serve as a powerful tool in unlocking the dynamics of complex systems.

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