Sankey diagrams, also known as flow diagrams or network diagrams, are a powerful and visually appealing tool for representing complex data flow in a simple and intuitive manner. Developed in the 19th century by William Rankine, they have since gained widespread adoption in various fields, from science and engineering to business and data analysis. By unlocking the power of Sankey diagrams, we can communicate intricate connections and processes with clarity and precision, making them an essential tool in contemporary data visualization.

What are Sankey Diagrams?

A Sankey diagram is a type of network diagram where links or bars represent quantities or values flowing between interconnected elements or variables. Each link has a specific weight, indicating the volume or magnitude of data passing through. Often used as a flowchart, Sankeys effectively highlight the direction and amounts of data exchange between different sources, processes, or outputs.

Creating a Sankey Chart

Creating a Sankey diagram is relatively straightforward and can be achieved using various visualization tools, including Excel, Tableau, D3.js, or any other data visualization software. The process involves the following steps:

1. Defining the nodes: Identify the starting and ending points in the flow, such as sources (inputs) and sinks (outputs). These are usually represented as circles, rectangles, or other shapes.
2. Estimating the flows: Determine the volume or value of data flow between these nodes. This can be quantitative data (numbers) or qualitative information (sizes or weights).
3. Creating the links: Each link connects a pair of nodes and represents the flow. For quantitative flows, you can use straight bars with varying lengths proportional to the flow amount. For qualitative flows, you might use arrows with custom widths.
4. Labeling and styling: Add labels for each node and link to provide context and information about the data.
5. Visual adjustments: Arrange the nodes and links in a visually appealing and readable way. You might need to use a layout algorithm or force-directed graph to optimize the placement.

Sankey Diagram Applications

Sankey diagrams find wide-ranging applications due to their ability to convey complex relationships in a clear and concise manner. Here are some key applications:

1. Process flow analysis: They are perfect for mapping supply chains, production processes, or any network with multiple steps and inputs and outputs.
2. Energy and resource transfers: In the environmental sector, Sankeys help visualize how electricity, water, or other resources are distributed and consumed.
3. Economic analysis: They can display trade flows, capital flows, or financial transactions between countries, sectors, or organizations.
4. Data storytelling: Sankeys can make a data story more engaging by illustrating the flow of information or decisions across a system or project.
5. Policy and decision making: Decision-makers can use Sankeys to understand the implications of different choices or interventions in a particular process.

Unlocking insights

One of the most powerful aspects of Sankey diagrams is that they help identify bottlenecks, leaks, or inefficiencies in a system. By highlighting the volume of data flowing through each link, you can quickly pinpoint areas where optimization may be necessary.

Conclusion

Sankey diagrams overcome the limitations of traditional linear graphs by visualizing data flow in a comprehensive, non-parametric way. Their ability to visualize complex connections through a visual hierarchy makes them a valuable tool in understanding and communicating data. Whether you are analyzing business processes, studying resource distribution, or designing data-driven solutions, unlocking the power of Sankey diagrams can help you make sense of intricate relationships and drive better decisions.

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