Have you ever been asked to compare multiple competitors, across multiple criteria? Perhaps you have needed to compare multiple products across varying functionalities. Radar charts, otherwise known as spider charts, can be useful tools for visualizing this type of data. Much like we discussed previously about pie charts, it is important to know when to use radar charts, because while they can be highly effective, they are not always the best choice.
Despite criticisms, radar charts have their place and can be used to visualize data quite well under certain circumstances, which we will outline here. At HelloInfo, we use radar charts in select situations, ensuring we leverage them only in places where they are best suited.
What is a radar chart?
The radar chart was first used by the mathematical statistician Georg von Mayr in 1877. These charts are used to represent multidimensional data in a 2D chart of three or more variables. Each variable in the radar chart has its own axis, also known as a spoke, which starts in the center. These connect to the node, which is the value of a variable, with a line to eventually form a polygon. It is easy to see why they are sometimes called a spider chart, owing to the spider web-like visualization they create. There are two types of radar charts: marked and filled. Marked charts include markers to represent each data point. Filled charts have the entire area of the chart filled with a color to help distinguish separate data points.
When to use a radar chart
Radar charts are best utilized for performance analysis, as they can clearly exhibit which variable in a data set is doing better than the rest. With multiple variables being presented in the chart, it can be useful for those who are using different metrics to make a decision. This highlights radar charts’ most distinctive feature; it provides a single image to compare all metrics. The downside to providing an image of all metrics is that the actual data is sometimes difficult to read. Therefore, radar charts are not suitable when a user is looking to display a high number of exact values. Instead, radar charts are most useful when a user is looking to display a variable that stands out. They can also show how different data points compare under the same variable.
It should be noted that users should not use a radar chart when representing time series data or measuring dimensions with distinct scales in order to ensure data clarity.
Pros and cons of radar charts
There are several advantages to using a radar chart to visualize data:
- They are the best method to use when making a decision by comparing multiple data sets simultaneously.
- Users can compare multiple variables or features using a radar chart.
- They can take up less space and be more visually appealing than other charts.
- The size and shape of the polygon created gives a clear summary of all variables being used.
- They can easily show stark variations or common characteristics in data.
There are also several drawbacks of radar charts:
- Comparing different quantities of values on different axes may be difficult as they may have a different measuring scale.
- This is more evident when plotting more than 3 sets of data as too many polygons can create a mess of data.
- Radar charts are harder to plot compared to other charts.
- With a radar chart one axes may cover up another, hiding some data.
Best Practices for radar charts
There are several things to keep in mind while using a radar chart:
- Think about the challenge of comparing things by area – People are good at comparing data one dimension at a time. Asking users to compare the relative areas, angles, and peaks of irregular shapes in a radar chart can be a challenge. Make sure not to visually overrepresent some areas.
- If presenting the radar chart live (for example, in a client meeting), gradually introduce it – Narrating and animating the radar chart piece by piece can help an audience understand the data before the chart becomes to dense.
- Order the axes consistently – To mitigate wildly different shapes and sizes of data, place meaningful data as close together as possible and use the same order every time for similar data sets.
- Consider alternatives – While radar charts are visually appealing and can lend some variation in a report, they may not be the right visual to use. Consider what message you are trying to convey and use an appropriate chart.
While radar charts can deliver key messages for comparisons from competitive analysis to product evaluation, they can also confuse readers. At HelloInfo, we use many different chart types to visualize data, including radar charts when appropriate. Sometimes it is necessary to create multiple data visualization options to determine which version will be most impactful for our clients’ needs.
If you are interested in learning more about how HelloInfo can support with your data visualization needs, please schedule a call with us.