The mekko chart (marimekko) is also known as a mosaic or matrix chart. Its name comes from a Finnish weaving company, known for the textures of its weaves.
It is similar to a column chart / treemap, where both its height and width represent information. They are used to represent sample data from different categories. The higher the data is, the greater the value.
How to interpret Mekko charts
While Mekko charts are great for representing category and subcategory data types, reading and understanding them is not straightforward.
In the chart above, the width of each vertical column (representing people’s hair color) is not the same. Therefore, the height of each block cannot be directly compared.
The area of each block correctly represents the data value. It is easier for us humans to compare heights than areas.
Therefore, those who are not used to Marimekko chart representations may have difficulties when interpreting it.
When should Mekko charts be used?
Mekko charts can be used in countless occasions. These are some of them:
Representing store sales
They enable sales data visualization.
Let’s suppose a company has an large chain of retail stores in various geographic locations. These stores sell items in different categories: furniture, electronics, and toys.
A mekko chart can easily represent store category data and the items that are on sale.
For example, the following chart shows sales data for a series of stores.
The total sales are divided between the different stores on the vertical axis, and on the horizontal axis we find the different categories.
This chart helps you visualize which store sold the most items and which item has the highest proportion of sales among all items.
Comparing budget breakdowns
These chart types are very useful for visualizing how different departments within an organization allocate budgets to different activities.
In the chart below, the vertical axis represents the departments: research, sales, and operations.
The horizontal axis represents how each department has divided their budget into various activities: human resources, travel, equipment, and promotions.
From the chart, it is clear that the budget of each department varies according to its functions and roadmap.
Representing market share across all categories
They are often used to represent how different companies participate in a multi-segment market.
The chart below shows the share of car companies across various car segments: convertibles, coupe, SUV, crossover and hatchback.
Representing a skills matrix
These charts are a great tool for visualizing the skill set and knowledge level of different for jobs.
For example, a Marimekko chart can represent key job titles and their related skills within an organization working with big data: developer, data scientists, statisticians, and researchers.
Common pitfalls when using Marimekko charts
Misinterpretation when comparing areas
Charts are interpreted based on the area of each rectangle. However, each rectangle differs in its aspect ratio.
It can be difficult to compare rectangle areas to understand which has a greater value.
For example, the chart below represents the number of employees who remained with the organization after a merger, and those who left the organization in two separate categories.
One group is a set of employees that received career guidance before the merger, and the other is one that did not receive guidance.
You can see that becomes challenging to understand the effectiveness of the career guidance program, as it is difficult to understand whether the green rectangle on the bottom left, or the orange one on the top right, is the largest, due to the different proportions of the rectangles when represented in a mekko chart.
Rectangles are not arranged along a common baseline
In charts with multiple categories, the rectangles representing a certain combination of variables are not arranged along a common baseline. It’s not easy to compare their length.
For example, it’s difficult to compare the heights of the highlighted rectangles in the chart below, as they don’t have the same baseline.
It becomes difficult to represent a large number of categories with this type of chart. When there are many categories on both axes, it is difficult to label them. The chart becomes fuzzy and difficult to interpret.
Marimekko chart alternatives
Marimekko charts work only when the number of categories is limited. Even if they have great aesthetics, they might not be easy to interpret. There are alternatives to Marimekko charts, which may be more intuitive.
Marimekko charts combine all the information obtained into one chart, but they can be misinterpreted by the untrained eye. It may take you many barcharts to represent the same data, but each separate one provides more clarity.
It may be necessary to cross-reference information to interpret all the data.
Stacked bar chart
They are suitable for category data when the verticals have the same aspect ratio. For example, if there are equal numbers of boys and girls in a class, the stacked bar chart is a more logical alternative to Marimekko.
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