Sankey with circular links
This example demonstrates a Sankey diagram that supports circular links, allowing flows to loop back to earlier nodes in the process. The chart uses the `d3-sankey-circular` plugin, built on D3 v4, to detect and draw cycles as curved paths rather than straight lines. Node positions are computed with the plugin’s layout, while links are rendered as SVG paths with a gradient stroke to indicate direction. The sample data models a multi-stage process with explicit feedback loops, such as from process1 back to process4, and includes twenty named nodes with numeric flow values.