What type of visualization is best for displaying hierarchical data?

The best visualization for displaying hierarchical data is a tree map. This type of visualization is designed to represent data organized in a hierarchical structure, allowing users to see the different levels of categories and subcategories effectively. Tree maps encode data dimensions using rectangles, where the size and color of each rectangle can represent different metrics. This visual representation makes it easy to understand not only the hierarchy but also the proportional relationships between the data points.

In contrast, scatter plots are used to show relationships between two continuous variables and are not suited for hierarchies. Pie charts, while useful for showing parts of a whole, do not convey hierarchical relationships clearly. Line charts are effective for displaying trends over time, but they do not provide a structure for illustrating different levels of data hierarchy. Thus, the tree map stands out as the most appropriate choice for visualizing hierarchical data.