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What is a Tree Map and what is it good for?

The treemap is a chart type used for visualizing information that displays a hierarchical data set (items are linked to each other). The structure is displayed in nested rectangles that decrease in size, and that make up its different levels.

This type of chart can accurately convey the relationship between the whole and its parts, even with complex data. It is especially useful for simultaneously expressing a wide variety of categories and subcategories.

Keep reading the post to understand more about treemaps and what they are used for.

Visual representation of the tree map

The mapping of this chart is similar to the branches of a tree, hence it’s name. It starts with a trunk that branches out into smaller branches. Larger rectangles are divided into smaller rectangles that represent the next hierarchy level.

tree map

Understand the elements/characteristics that make up a Tree Map:

  • Rectangles are used for representing data;
  • Each rectangle represents up to two numerical values. They can be called “nodes” or “branches” and their sets are called “leaves”;
  • The size and color of the rectangles are calculated according to the quantitative variables associated with the representation.
  • Data is laid out in multiple layers, with categories (parent elements) subdividing into subcategories (child elements). Child elements are rectangles nested within their parent element’s rectangle;
  • The area of the parent category is made up of the sum of its child categories;
  • The rectangles are arranged according to their dimensions, so that the top left corner has the largest rectangle, while the bottom right corner of the chart has the smallest rectangle.
  • A treemap chart does not represent the variation of datasets in magnitude.
  • Values must be positive. Negative values are not represented.

What are Tree Maps good for

Treemaps are designed to represent a large volume of hierarchical data in a compact, attractive and easy-to-understand way. The intention is that the user can easily discern the patterns and compare them intuitively.

The big advantage treemaps offer is the possibility of providing a quick overview of the hierarchical structure of large amounts of data without taking up a lot of space on the screen. Treemaps are also great for comparing ratios between categories. Here are some examples where treemaps can be used:

  • Showcase the increase in population density of a country and its subdivisions (region, district, city, etc.);
  • Showcase development rates (education, basic sanitation, healthcare access, etc.) within districts that belong to a larger geographic area;
  • Compare the sales performance of different companies or business models over a given period;
  • Inventory of animal and plant species in a given biome, divided by class, genus, species;
  • Comparison of the volume of rainfall by period in a city, divided by neighborhoods;
  • Comparing website access metrics, purchases made, costs per click, average tickets value, among other KPIs used in marketing strategies

pet shop tree map

Even with some limitations, treemaps are among the chart types that best represent data that has some kind of hierarchy attached to it. It is a rich analysis tool, capable of providing a large amount of information, in a compact and easy-to-understand manner.