Sankey charts, often referred to as data flow diagrams or energy diagrams, have gained significant traction in the fields of data visualization and information graphics. These visually appealing and intuitive illustrations effectively convey complex flows of information, making them a valuable tool for understanding and presenting data patterns. In this article, we will delve into the fascinating world of Sankey charts, exploring how to create them and the diverse applications where they shine.

What Are Sankey Charts?

Sankey diagrams were first introduced by the 19th-century engineer William Sankey to visualize the flow of energy in systems. They capture the directional relationship between different elements, or “nodes,” and their respective shares or proportions. In data visualization, these charts have been adapted to display various types of flow patterns, from financial transactions to supply chains.

A classic Sankey chart consists of a series of interconnected links or arrows whose lengths represent the quantity or value of the flow. Each arrow head points from a source node to a target node, while the thickness of the link indicates the relative amount. This layout allows users to easily compare the flow between different paths and identify bottlenecks or inefficiencies.

Creating Sankey Charts: The Basics

Creating a Sankey chart in a tool like Tableau, PowerBI, or any data visualization library is a straightforward process:

1. Choosing a Data Source: Start with a dataset that contains the information on your flow, such as the origin, destination, and quantities. If you’re dealing with time intervals, separate the data into distinct time periods or snapshots.

2. Select the Data: Choose the fields that relate to your nodes (sources and targets), quantities, and any attributes you want to display, such as colors or labels.

3. Set Up Nodes: Define your nodes (sources and targets) and associate them with the appropriate fields. You can also add attributes like icons or colors to enhance the visual representation.

4. Draw the Links: Map the flow by connecting the nodes with links, proportionally representing the magnitude of the flow. Make sure to label each link with clear text to indicate the quantity.

5. Format and Style: Customize the appearance with a suitable color scheme, grid, and annotations to enhance readability and comprehension.

6. Interactivity: If applicable, incorporate interactive features like tooltips or filtering options to allow users to explore specific data points or segments.

Applications of Sankey Charts

Sankey charts find widespread use across various domains due to their ability to visually convey intricate flow patterns:

1. Resource allocation: In business and finance, they help track and compare investment, expenditure, or production across different departments or projects.

2. Network analysis: They aid in understanding the dependencies and interactions between different entities in a system, such as supply chains, communication networks, or transportation infrastructure.

3. Energy and environmental studies: In energy flows, Sankey diagrams can assist in assessing the efficiency of renewable and conventional sources, monitoring carbon emissions, or analyzing energy transfers.

4. Policy mapping: Sankeys can visualize government policies, regulations, and funding allocations to identify areas of impact and allocate resources more effectively.

5. Transportation planning: They can display modes of transportation (e.g., car, train, airplane) and their relative contributions to a journey, helping in urban planning and traffic management.

6. Public health and infectious disease tracking: In the context of disease outbreaks, Sankey diagrams can visualize the flow of patients between locations and help identify risk factors.

Conclusion

Sankey charts have evolved beyond their original utility in energy management to become a versatile data visualization tool. By visually representing flow patterns, they facilitate a deeper understanding of complex systems and processes. Whether you’re analyzing financial data, mapping supply chains, or exploring environmental phenomena, consider incorporating Sankey charts into your analysis to communicate your insights in a clear and compelling way. Happy exploring!

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