SankeyDiagramme

SankeyDiagramme, commonly known as Sankey diagrams, are a type of flow diagram in which the width of the arrows is proportional to the magnitude of the flow. They are used to visualize energy, material, or cost flows within a system, showing how inputs are transformed and distributed. The diagrams emphasize major transfers and losses, making inefficiencies or bottlenecks visually apparent. A typical SankeyDiagramme starts with one or more source nodes on the left, with flows converging or splitting as they move to destination nodes on the right. The sum of inflows equals the sum of outflows, though in some contexts losses or unused fractions are shown as separate downstream flows. Colors are often used to distinguish categories, while labels can provide quantitative values.

Historically, the Sankey diagram was named after Captain Matthew Henry Phineas R. Sankey, who used the format in 1898 to depict energy efficiency in steam engines. Since then, the method has been widely adopted in engineering, environmental studies, energy policy, and corporate reporting. Modern tools support interactive or static SankeyDiagramme, including D3.js, Plotly, and various business intelligence platforms; they allow dynamic filtering, re-aggregation, and automatic layout optimization.

Limitations include potential overplotting with many categories, misleading emphasis if not normalized, and the fact that exact flow values can be hard to compare when many paths converge. Effective use requires careful labeling, appropriate aggregation, and consideration of the viewer’s ability to interpret relative thickness.