Sankey charts are a type of flow visualization used to represent data dynamics, such as the movement and distribution of resources, energy, or information. These charts are named after the Scottish engineer, Matthew Henry Phineas Riall Sankey, who developed this graphical representation in the late 19th century to depict the energy loss in steam engines. Today, Sankey charts are widely used for various applications, including data analysis, energy systems, material flow analysis, and more. This article will cover the creation and applications of Sankey charts, highlighting their utility in visualizing complex data flows and their underlying dynamics.
Creating Sankey Charts
Step 1: Choosing the Data
Sankey charts require data that includes the quantities and sources or destinations of the flows. For instance, in a material flow analysis within a manufacturing plant, this would involve data on raw materials entering, intermediate products moving between processes, and final products exiting the facility.
Step 2: Plotting the Node
Node nodes are placed on the horizontal axis and represent the start or end points of the flows or stages within a process. Each node is connected by bands or arrows, which represent the quantities of the flows.
Step 3: Drawing the Bands
Bands or links between nodes are the most crucial component of a Sankey chart. They need to be proportionally sized to reflect the flow quantities. Typically, the thickness of the bands is used to indicate the magnitude of the flow.
Step 4: Color Coding
Color coding by category or stage helps distinguish different flows, which enhances readability and interpretation. Using colors intelligently can also highlight important data, such as dominant flows or bottlenecks within the system.
Step 5: Layout and Formatting
Sankey charts can have various layouts, including treemaps, circular layouts, and parallel flow diagrams. Choosing the right layout depends on the data size and complexity. In addition to layout, appropriate labels, legends, and tooltips can greatly enhance the chart’s clarity and usability.
Step 6: Implementing Tools
While it is possible to create Sankey charts manually using basic graphing tools or drawing software, various software tools and programming libraries make the process much easier and more efficient. Popular choices include Microsoft Excel, Tableau, Python libraries like matplotlib, seaborn, and pySankey, and dedicated software such as Vizlib Sankey.
Applications of Sankey Charts
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Energy Systems – Sankey charts are often used in the energy sector to visualize the flow of energy from various sources to end-users or across processes. For example, analyzing energy consumption within a building or the distribution of electricity in a power grid.
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Data Flow Analysis – In digital product design and analytics, Sankey charts help understand the journey of user interactions in a system, tracking steps from engagement to conversion.
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Material Flow Analysis – In manufacturing and logistics, these charts assist in identifying inefficiencies and opportunities for waste reduction, by visualizing where materials enter, move through, and exit the system.
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Financial Flows – Tracking investments, cash flows, or revenue streams across various departments or regions within an organization can benefit from the clarity and insight a Sankey chart provides.
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Web Traffic Analysis – Online stores can use Sankey charts to visualize user traffic flows across different pages, highlighting which parts of a site are most popular and where users tend to drop off.
Conclusion
Sankey charts are invaluable tools in the visualization of complex systems and processes, offering a comprehensive view of data flows with a unique blend of aesthetics and functionality. Whether examining energy consumption patterns, optimizing product design, or dissecting user navigation on a website, these charts enable data analysts, developers, and designers to uncover insights, manage resources, and guide decision-making processes effectively. As computational and graphical tools continue to evolve, the practical applications and impact of Sankey charts are only set to expand, making them an essential part of any data analysis arsenal.
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