Visual Viability: Mastering Sankey Charts for Efficiency Insight

Introduction

Data visualization is essential in modern data analysis, as it allows complex information to be presented in a format that is both intuitive and actionable. Among the many types of data visualizations available, Sankey diagrams are a unique and powerful tool for understanding systems, processes, and flows. They help to visualize the efficiency of various elements within a system, making them valuable for efficiency auditing, resource allocation, and strategic planning. This article delves into the creation of Sankey charts and their myriad applications across various disciplines.

Understanding Sankey Charts

Sankey diagrams are named after their inventor, Henry Darcy, a French engineer. However, they were popularized by Max Schultze and are named after a later, more visible proponent, William Playfair’s son-in-law, Dr. Martin Sankey. These charts are characterized by their distinctive arrows, which are fanned to represent the energy, material, or flow within a system. The thickness of the lines indicates the quantity of the flow. They are also distinguished by their non-zero-sum quality, where a component can begin and end on different sizes of lines, representing the quantity of flow into and out from that component.

Key Characteristics of Sankey Charts

1. Directional Flow: Sankey charts are designed to follow the flow of energy, material, or processes.
2. Quantitative Representation: Flow thickness conveys the magnitude of the substance or energy.
3. Non-zero Sum: Sankey diagrams can depict a system with different flow volumes into and out of each element, which makes them well-suited for depicting complex systems that may not balance out perfectly.
4. Hierarchical Structure: They often represent systems in a hierarchical manner, allowing users to see the details of each sub-system within the context of the larger whole.

Creating Sankey Charts

Creating a Sankey chart can be a daunting task due to the complexity of the data required and the specific tools needed for its construction. However, the following provides a basic guide on how to create one using common software tools:

Software Options

• Excel: The latest version of Microsoft Excel offers some functionality for basic Sankey chart creation.
• Power BI: An advanced data visualization tool that includes several options for creating Sankey diagrams.
• R and tidyverse: A robust open-source option for creating detailed Sankey charts through programming.
• Tableau: A powerful data visualization tool that supports Sankey diagram creation with various options for editing and customization.

Creating a Sankey Chart in Excel

1. Prepare Your Data: Organize your flow data in a table, ensuring there is continuity of flow from one element to another.
2. Insert the Chart: Once you have your data ready, select it and choose “Insert” > “Recommended Charts” > “Sankey Chart.”
3. Customize the Chart: Personalize your chart as needed with colors, shapes, and other formatting options.
4. Analyze and Refine: Once constructed, the Sankey chart should be carefully analyzed to discern trends or inefficiencies within your system.

Applications of Sankey Charts

Sankey diagrams are particularly useful in situations where a detailed flow of materials, energy, or funds is required:

Energy and Environmental Analysis

• Greenhouse Gas Emission Analysis: Visualizing carbon flows helps in identifying areas of high emissions.
• Solar and Wind Energy Systems: Sankey charts can illustrate the energy loss at each stage of production within these systems.

Business and Economic Models

• Financial flows: Tracking and analyzing money moves from one account to another within a company.
• Supply Chain Efficiency: Representing the movement of raw materials through the production process to finished goods.

Systems Engineering

• Process Optimization: Visualize the flow within a production process to identify bottlenecks.
• Transport Networks: Illustrative of traffic flow or the movement of goods via various transportation modes.

Public Sector and Policy Analysis

• Public spending: Representing government expenditures across different areas or programs.
• Policy Impact: Visualizing the flow of policy measures or regulations and their effects on various stakeholders.

Conclusion

Sankey charts can transform complex and potentially dense data into visually insightful representations that are not only informative but also engaging. Their ability to show quantities and flows with precision and sophistication makes them a critical tool in data visualization. By mastering the creation and analysis of Sankey charts, professionals can enhance decision-making, identify inefficiencies, and chart courses toward greater efficiency and sustainability. The next time you find yourself needing to present or analyze complex system flows, consider the Sankey charts as your go-to visual tool.

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