Mekko Chart
A Mekko chart, also known as a Marimekko chart, is a two-dimensional stacked bar chart.
What makes it unique is that both the width and the height of the bars are proportional to the data they represent. This allows you to visualize and compare the magnitude of different segments within and across categories simultaneously.
An example of an embedded Mekko chart
Definition and Description
A Mekko chart consists of a series of adjacent columns, where:
- Width of the column: Represents the proportion of a whole for a particular category. The wider the column, the larger the overall size of that category.
- Height of the segments within each column: Represents the proportion of a sub-category within that larger category. The sum of the heights within a column equals the total height of that column.
- Area of each segment: Is proportional to the absolute value of that sub-category. This is the key differentiating factor of a Mekko chart.
Essentially, a Mekko chart visualizes a contingency table where both row and column totals are meaningful and are represented by the dimensions of the rectangles.
How to Create an Effective Mekko Chart
Creating a clear and insightful Mekko chart requires careful planning and execution:
Organize Your Data
Your data should typically consist of three variables: two categorical variables (defining the columns and segments within columns) and one quantitative variable (determining the width of the columns and the height of the segments).
Calculate Proportions
Before plotting, you’ll need to calculate the proportions for both the width of the columns (relative to the total of the first categorical variable) and the height of the segments within each column (relative to the total of that specific column).
Order Your Categories Strategically
The order of the columns and segments can significantly impact the readability and insights derived from the chart. Consider ordering by:
- Size: Arranging columns from largest to smallest (based on width) or segments from largest to smallest within each column.
- Logical Flow: If there’s a natural sequence or hierarchy in your categories, maintain that order.
- Highlighting Trends: Order categories to emphasize specific patterns or comparisons you want to draw attention to.
Choose Distinct and Meaningful Colors
Use a color palette that allows for easy differentiation between segments. Avoid using too many similar colors. Ensure the colors you choose don’t carry unintended connotations.
Label Clearly and Concisely
Label each column and segment clearly. Use appropriate font sizes to ensure readability. If space is limited, consider using abbreviations or a clear legend.
Include a Clear Legend
A well-designed legend is crucial for understanding which color corresponds to which segment.
Add Value Labels (Optional but Recommended)
Displaying the percentage or absolute value within each segment can enhance the precision and interpretability of the chart. Choose a labeling strategy that doesn’t clutter the visualization.
Provide a Meaningful Title
The title should clearly and concisely describe what the Mekko chart represents.
When to Avoid Mekko Charts
While powerful, Mekko charts can be less effective in certain situations:
- Too Many Segments: If you have too many small segments, the chart can become cluttered and difficult to read. Consider grouping smaller segments into an “Other” category.
- Focus on Precise Values: If the primary goal is to communicate exact numerical values, a table might be more appropriate. Mekko charts emphasize proportions and relative sizes.
- Negative Values: Standard Mekko charts are not designed to handle negative values effectively.
- Difficulty in Creation: They can be more complex to create than standard bar charts and may require specialized tools or manual calculations.
- Potential for Misinterpretation: Due to their complexity, ensure your audience understands how to interpret the width and height dimensions. Clear explanations and labels are crucial.