What is a bubble chart?
A bubble chart is an effective data visualization tool which has the potential to compress large datasets for hundreds and thousands of data points in a single view.
Unlike traditional charts, bubble charts add a third dimension to visualize data. It represents data in 3 numeric data dimensions, where X and Y axis are separate variables. Each plotted point represents the relationship between data by the area of its circle as the third visual dimension.
A bubble chart has the capability of accommodating even 4 and/or 5 dimensions of data, a fourth data set will become the bubble’s label and a fifth will be a category to differentiate data points using separate colors.
When to use a bubble chart
Bubble Chart, like other visualization tools, is a form of storytelling. It represents the relationship between data using the position and proportion of the plotted bubbles.
The Bubble Charts is particularly helpful to understand data sets with multiple variables, visualizing patterns, and identifying trends using data analysis. It is an excellent tool to picture marketing and sales/finance scenarios.
For example, comparing returns on investment, over a period of time, for various categories such as stocks, mutual funds, bonds, etc. Bubble Charts make it easier to present a story as a visual element by finding a correlation for a data series and analyzing the patterns.
How to create a bubble chart
We will create an example Bubble Chart using Chartio, a self-service business intelligence tool for cloud analytics.
Similar to every chart, the first step is to gather data and choose the categories that are most important to represent.
For this example, we will use data from the UFO Sightings data source that comes with Chartio and details the count and nature of different sightings of UFOs.
Here’s a step by step process of creating a Bubble Chart using Chartio –
- Click ‘Explore’ on the top left in the navigation bar to start exploring your data. (Typically, a chart type is automatically selected based on the data selected. If you want a specific chart, pre-select it from the chart type. This gives a brief description of how to arrange your data.)
- Use the Data Source (These sources are connections to your external data such as databases and CSV files) dropdown to select the data source you want to use to build your chart. Select UFO Sightings. Each table in the selected data source is listed in the sidebar and can be expanded to view its columns. Click Sightings.
- Drag a field (such as ID and Duration) to Measures. Measures aggregate your data using math functions such as Sum of Data. Drag Id into the Measures field. Click it to open its settings, and change the Aggregation to Count of Distinct Sightings. Change the label accordingly, then click Ok. Likewise, drag Duration into the Measures field. Click it to open its settings, and change the Aggregation to Total Sum of Sightings. Change the label accordingly, then click Ok.
- Drag a field (such as Shape) to Dimensions. Dimensions group your data, such as by Date or Product Type. Drag Shape into the Dimensions field. Click it to open its settings, and Sort them in Ascending order. Change the label accordingly, then click Ok.
- Drag a field such as Created Date to Filters (it is an optional step, depending on your data set.) Filters set a condition to allow you to filter through your data. For example, when you drag Created date, click on it and select between and set a date range, then click Ok. In this example, we do not use any filter.
- Click Run Query. You can change the Chart Title or even review Chart Settings.
- Click Save Chart. You can further add more layers or even transform data in addition to the above steps. (NOTE – Refer to the basic chart and snapshot below for an overview of chart creation. You can hover the cursor on the bubble to review the label)
Best practices for creating bubble charts
- To enhance the impact of a bubble chart at least 3 dimensions of data are essential otherwise, any other traditional charts such as bar charts, column charts or line charts can do the job.
- Although bubble charts can compare more data, the number of categories that can be mapped on are limited. The use of colorful bubbles might be tempting, but too many of them in one chart would look chaotic.
- It is important to set a maximum bubble size since it is critical to a user to accurately interpret data, especially if the data range is spread out over a specific axis. It is the area of a bubble that conveys the meaning, not its radius or diameter.