Flow Visualized: The Alluring Artistry of Sankey Charts
In the world of data visualization, where figures and information are translated into images that tell stories and make complex systems comprehensible, Sankey diagrams stand out as a captivating medium. A type of flow diagram, Sankey charts are visually stunning and reveal the intricacies of energy, materials, or finances through the flow of “streamlines” that expand or narrow according to the quantity of flow. Here we delve into the creation of Sankey charts, their applications, and the reasons they are such a powerful way to represent information.
The Art of Sankey Chart Creation
Sankey diagrams are named after their inventor, William Playfair, who created the first examples in the early 19th century. They were originally used as a way to visualize the efficiency of energy flows in thermodynamic processes, and today, their utility spans across many sectors.
Creating a Sankey chart involves the following steps:
1. Gathering Data
The first stage is to gather all the relevant data. This could be for energy use, material flows, or financial transactions. It’s imperative to have accurate and complete data as any errors can lead to skewed representations.
2. Quantifying Flows
Next, you must measure the amount of material or energy that moves from one process to another. These flow values are typically normalized to a common scale to ensure that the chart remains consistent and readable.
3. Determining the Streamlines
Sankey charts consist of arrows—streamlines—that trace the flow of matter or energy from an input to an output. The width of each streamline represents the size of the flow, and the width is typically proportional to the absolute or relative quantity being depicted.
4. Streamline Placement
The placement of the streamlines within the diagram also plays a crucial role. Each streamline flows from the source to the destination, and streamlines originating from the same process or component typically converge or diverge smoothly.
5. Linking Nodes
Nodes are the points where streamline meet—either to represent a process, a point where something is converted or where flow is split or summed. Careful placement of nodes and streamlines ensures that the chart accurately reflects the processes being analyzed.
6. Esthetics and Aesthetics
Last but not least, the design of the Sankey chart—colors, font, and layout—must be deliberate to enhance the chart’s readability and visual appeal. Streamlines flow efficiently without unnecessary twists, and a palette of colors can highlight key aspects of the data visualization.
Applications of Sankey Charts
The versatility of Sankey diagrams is one of their greatest strengths. They are widely used in various fields, including:
Energy flow analysis
Sankey charts are exceptionally useful for visualizing energy transfer within a system. They help in understanding how energy is used efficiently or wasted and can identify areas in the system where improvements can be made.
Logistics and supply chain
Logistics departments leverage Sankey charts to reveal patterns and bottlenecks in supply chain efficiency. They allow for a clear visualization of material and product flows throughout the supply chain.
Financial analysis
Financial institutions use Sankey charts to illustrate the flow of funds across different financial activities. This is particularly helpful in illustrating the effectiveness of investment portfolios or the allocation of funds among various projects.
Environmental assessment
Sankey diagrams can make environmental footprint assessments more intuitive. They help visualize the flow of carbon emissions, pollutants, and resources, thus providing valuable insights into sustainability efforts.
Conclusion
Sankey charts are not just an art form but a functional design tool that enhances understanding of complex processes. They offer a unique way to represent information by highlighting the magnitude of flows between different points or processes. Their clarity and the insights they reveal make Sankey charts an invaluable part of a data visualizer’s toolkit. With advancements in data visualization software, creating and interpreting Sankey charts has never been easier, making them a staple in many sectors for years to come.
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