Unidirectional node-link diagrams are commonly referred to as trees. They display the topology of a hierarchy using marks for nodes and links. Nodes are usually rendered as dots, circles, rectangles, or some other symbol, and links are usually the lines that connect the dots. In some trees, only the leaf and root nodes are rendered, or only the links are displayed.
The following diagrams are examples of node-link diagrams created with D3. You can download the full code and data for all examples from the GitHub repository for this chapter:
A dendogram showing the main tributaries of the Amazon river. Code: Examples/dendogram-5-amazon-river.html.
The next illustration is a radial dendogram displaying the names of all the countries in the Eurasian supercontinent, classified by continents (Asia and Europe) and United Nations regions. The data is...