An Alternative to Tree-Maps

https://www.nngroup.com/articles/treemaps/

Treemaps are a data-visualization technique for large, hierarchical data sets. They capture two types of information in the data: (1) the value of individual data points; (2) the structure of the hierarchy.

Example of a treemap from https://help.tableau.com/current/pro/desktop/en-us/buildexamples_treemap.htm

Definition: Treemaps are visualizations for hierarchical data. They are made of a series of nested rectangles of sizes proportional to the corresponding data value. A large rectangle represents a branch of a data tree, and it is subdivided into smaller rectangles that represent the size of each node within that branch.

Alternatives:

Treemaps should not be used if your data is not hierarchical: in those situations, they are functionally equivalent with a pie chart — simply showing a parts-to-whole relationship. (Pie charts are not great visualizations either — like treemaps, they are based on area and angle, attributes that are not preattentive. They should be used only to communicate that one or two items are much larger than the rest, and not for comparing relative sizes of the pie slices.)

• Scatterplot: A scatterplot is often a better choice than a treemap for visualizing data with 2 quantitative variables, as the human visual system can quickly and accurately detect 2D position. This scatterplot also adds a third, categorical variable, expressed in color.
• Use Bar Charts at Low Density, Treemaps at High Density: Bar charts resulted in significantly lower error when comparing leaf nodes at low densities. If a data set has only a few hundred elements, bar charts are more effective than treemaps.

Summary

• While treemaps can be useful for visualizing certain types of complex, hierarchical data sets, they often hard to interpret.
• If using a treemap, visually separate the different high-level categories, avoid using multiple colors to express numeric values, and design with color-blind users in mind.
• Understand what your users need to do with your data and consider whether other visualizations (such as a bar chart or a scatter plot) could replace or augment the treemap.