Sankey diagrams, named after their inventor, engineer Harold J. “Doc” Sankey, are a powerful tool in visualizing data flow between processes. These charts are widely used in various fields such as engineering, sustainability, finance, and healthcare to display the distribution of data across different mediums. Sankey diagrams are ideal for depicting flows from one set of entities to another, where the amount transferred between each pair of entities is represented by the width of the arrows. In this article, we’ll explore how to create Sankey diagrams to unravel insights and the diverse applications of these charts in unraveling complex data narratives.

The Essentials of Sankey Chart Creation

Creating a Sankey diagram involves mapping entities from one system to another. Each arrow width corresponds to the quantity being mapped from one set of entities to another. Sankey diagrams are particularly effective in visualizing quantities of data transferred between multiple sets of entities. Here’s a step-by-step guide to creating one:

1. Data Collection: Gather the data on each entity or process flow. This could be energy usage in a building, financial transactions in a bank, or carbon emissions.

2. Data Processing: Organize your data into a table with three columns: the source, the destination, and the value of the flow (e.g., amount, temperature, or amount of money) or proportion.

3. Choosing the Right Software: There are various tools available for creating Sankey diagrams, including manual tools like Excel and more sophisticated graphical software like Python’s Matplotlib or R’s ggplot2. For beginners, using tools like Tableau or SankeyMATIC can simplify the process.

4. Designing the Diagram: Arrange your entities in a way that makes sense for your narrative. The source of your data (e.g., electricity input) should be on one side, and the destination (e.g., electricity output) should be on the other. This arrangement helps in visual clarity and readability.

5. Finalizing the Arrows: Assign the width of each arrow to the value of the flow. This scaling is crucial for correctly interpreting the diagram. Sankey diagrams become misleading when the width of the arrows is not proportionate (i.e., when one arrow is much wider than the others without proper scaling).

6. Adding Labels and Legends: Include the names of your entities with proper labels. A legend that explains the scale or source/destination of each arrow is essential for clarity.

Applications of Sankey Diagrams

Sankey diagrams have a broad range of applications across different domains:

• Energy and Climate Research: They are used to map the energy efficiency of devices or to track the carbon footprint of products.
• Agricultural Operations: Sankey diagrams can represent the nutrient flow in agricultural systems, highlighting the efficiency of nutrient use and loss.
• Financial Markets: Portfolio analysis and wealth distribution can be visualized to understand investment performances.
• Healthcare Operations: These diagrams can show the input and output of various resources (e.g., doctors, nursing staff, surgical equipment) in clinical operations.
• Educational and Research Initiatives: They can depict the flow of grants, research funding, and publications within academic institutions or research networks.

Conclusion

Sankey diagrams are a valuable tool for unraveling complex data narratives, offering a dynamic visual language to understand the flow of information across multiple dimensions. By scaling the widths of the arrows proportionately, these charts ensure that the information they convey is both accurate and easy to interpret. As technology advances, we can expect to see more innovative uses of Sankey diagrams in various fields, helping stakeholders make informed decisions based on the insights they reveal. Whether you’re an engineer analyzing energy flow in a building or a researcher mapping the flow of ideas across academic disciplines, Sankey diagrams are a powerful ally in your data visualization toolkit.

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