Data visualization using colorful dots is no doubt visually appealing and a creative statistical graphing method. But do you know something that is more visually appealing? Bubbles.
Bubble charts use multiple bubbles (or circles) to display data points in a 3-dimensional space. However, the interesting thing about this 3-dimensional display is that the third dimension is represented through the size of the bubble.
Although quite different from other dot-like graphing methods, like the others, it is of various types, has real-life applications and can also be plotted using Excel. The rest of this article will see us trying to dissect the intricacies of a bubble chart and guiding you through how to make one yourself using Excel.
What is a Bubble Chart?
A bubble chart is a multivariable graph that uses bubbles to represent data points in 3 dimensions. Also known as a bubble graph, it has various applications in social sciences, economics, medicine, and other mathematical sciences.
As the name suggests, it represents data points with bubbles. Just like the dot plot, it is also a variation of the scatter plots, but replaces the dots with bubbles and also displays the values of 3 quantitative variables.
The 3 variables are displayed with 2 of the variables determining the data point that corresponds to the value on the horizontal and vertical axis. The third variable, on the other hand, corresponds with the size of the bubble.
Types of Bubble Charts
Bubble charts have various uses in different aspects of applied mathematics and statistics. These uses happen to vary not only with the kind of problems they solve, but also give rise to different variants of bubble charts.
This is due to the fact that the representation of the bubble chart needed to solve problems in each field differs from the other. Discussions in this section will cover each of these variants, including a diagram showing how they look.
To further aid our discussion on Bubble Chart variations, let us consider the table below which displays some information about the students of a school.
Simple Bubble Chart
Simple Bubble Chart is the most basic bubble chart variation there is. In the real sense, the simple bubble chart is not a variation of the bubble chart.
It is the original version of the bubble chart generated using Excel. This illustration shows only the first three numerical columns of the data in the table above.
In this case, we are dealing with only 3 variables, which is the simplest a bubble chart can have. The 2nd column (Number of Students) represents the horizontal axis, 3rd column (Average Score) represents the y-axis, while the size of the circle was determined by the 4th column (Math Average).
NOTE: The values used in generating this chart, is slightly different from the ones shown in the table above. You can also create different variations using the random number generator function in Excel.
Labeled Bubble Chart
The labeled bubble chart is also very simple but has little variations. Very similar to the simple bubble chart, the difference is that the bubbles on this chart have a label.
These labels are substitutes for legends. They are used in identifying the variable each bubble represents.
Bubble labeling is only feasible when dealing with a 3- variable bubble chart with very few data sets, just like in the illustration below. If the dataset is large, it is usually time-consuming and the chart becomes cluttered.
Multivariable Bubble Chart
This bubble chart variation is used when dealing with multiple variables that are more than 3. It helps to visualize different groups of variables with the help of colors.
You will notice that in the first 2 graphs illustrated above, the bubbles have only one color. But in the illustration below, there are three colors, with each color representing the group of the variable under consideration.
Here, we illustrated the different Sex, namely; Male, Female, and Others. This graph was obtained by plotting the data in all the 10 columns present in the dataset.
The graph was also obtained from a randomly generated value different from the one in the table above.
Map Bubble Chart
As the name implies, this bubble chart variation is illustrated on maps. It is usually used in geographical sciences, and are sometimes called cartograms.
The bubbles represent a geographical location on the map. For example, when plotting a map that requires you to identify places with crude oil, gold, and some other mineral resources in the world, you use the Map Bubble Chart.
The x and y axes will be plotted using the latitude and longitude of these places, then the landmass will represent the size of the circle.
The size of the bubble should tally with the size of the graph on which it is being plotted. This will ensure that each location is well recorded
3D Bubble Chart
This is a 3-dimensional variation of the bubble chart. In this case, we no longer have circle-like bubbles but have sphere-like bubbles.
The radius of the sphere is determined by the 3rd parameter in the dataset. This 3-dimensional bubble chart can also exhibit all the variations mentioned above.
However, it is not always advisable to use a 3-D bubble chart to visualize data. This will affect the visual appeal of the bubble chart.
Uses of a Bubble Chart
- Search Engine Marketing
Search Engine Marketers can easily determine the effect of a high Cost Per Click rate on the ad position, clicks, and website conversions. A bubble chart will help determine if there are significant improvements in these factors.
By plotting the number of clicks on the x-axis, the cost per ad on the y-axis, and the increase in conversion rate will determine the size of the bubble.
- Keyword Density
When working on Word Graphs, keyword researchers can use it to determine the density of a particular keyword or hashtag. An example is the Google yearly report of the most searched words.
This report can be made into a bubble chart, with the most searched occupying the biggest space on the map. This will make it easily identifiable.
- Promotional Effect
You can study the effect of promotions and adverts on your business using a bubble chart. The x-axis can have the number of adverts created, y-axis should have the cost spent on each ad, while the circle radius will translate to the revenue generated.
Bubble Chart Examples
Bubble Chart Question Example: Consider the table below, representing the birth rate, death rate, and GDP of 5 countries. Use this information to construct a bubble chart. Hence, use this chart to determine the country with the highest GDP and explain how you arrive at this conclusion.
Solution: The corresponding bubble graph for this data is illustrated below, and it was constructed using Excel.
The country with the highest GDP is Australia. We arrive at this conclusion from the size of the bubbles.
The graph was plotted with the Birth rate on the horizontal axis, the Death rate on the vertical axis, and the GDP determines the size of the bubbles. Hence, the country with the biggest bubble has the highest GDP.
It is clear from the graph that our answer is Australia.
Example 2: Use the graph generated from Example 1 above, to determine the country with the lowest GDP.
Solution: The country with the lowest GDP is Ireland. This is clear from our observation that the circle representing Ireland is the smallest on the Chart.
How to Create a Bubble Chart with Excel
Follow these steps to create your own Bubble Chart with Excel.
We will be using the table in Example 1 above to create our own bubble Chart in Excel.
- Step 1: Enter your data into the Excel worksheet.
- Step 2: Highlight the cells containing the data as shown in the diagram below. Go to Insert>Charts>Other Charts|Bubble
- Step 3: Double-click on the first bubble and a dialog box like the one shown below will pop up. Go to solid fill, then edit the color and transparency of the circle, (See Diagram)
Do this for each of the circles by changing the color as you please. You should, however, try to make sure the transparency is uniform.
- Step 4: Edit the layout of the graph, and add Chart titles, axis titles, changing the legend to the name of each country, etc.
- Step 5: Right-click on the graph, then go to Select Data. A dialog box similar to the one below will show up. Click on Series1, then Edit. Change the series name to Australia.
Click on the Add Button to add another series. This time, name it China. Do this for all the countries, and you will see your Legend change automatically.
In the solution we created earlier, the scale of the circles was reduced. You can also decide to reduce or even increase the scale for this graph by right-clicking on the graph, then going to Form Data Series.
Go to Series Options in the resulting dialog box, then scale bubble size as you please.
Tips for Creating a Bubble Chart
Here are a few tips for you to follow when creating a bubble chart.
- Limit Plot Data Points
Most times, bubble plots tend to overlap when it is being plotted on the graph. Therefore, it is good practice to always increase the transparency of the bubbles.
This will help ensure that some bubbles are not hidden, making it difficult for the reader to interpret. However, this does not completely solve the problem of cluttering and the inability to read data points.
The bubbles may still end up overlapping multiple times, till the transparency of the circles become ineffective. Transparency is great for readability, but it still has limitations.
- Include a Legend
Legends are to a bubble chart as the key is to the ignition. Just like, you can't start a car without the key, you can't read a multivariable chart without the legend.
The legend is what tells you the meaning of each color on the graph. In the example we treated earlier, if we didn't have a key, there was no way we could have been able to identify Australia as the country with the highest GDP.
Alternatively, you can label each bubble with their names to make it readable. This may, however, be infeasible when dealing with a large dataset.
- Present a Clear Trend
One of the most important parts of creating any graph is making sure it is readable. Your bubble chart should be interpretable by readers without putting in too much effort.
It should be able to present a clear trend with the bubble size as an indicator. Before finalizing your chart, try to experiment with the order in which the variables are implemented.
That is, if the variables are p1, p2, p3, you can experiment by plotting the chart (x,y,z) as (p1, p2, p3), (p2, p1, p3), …, making all the 6 permutations. You can now choose the best fit from these charts.
- Dealing With Negative Values
Variables that take negative values cannot directly translate to point size on the bubble chart. Therefore, one of the simplest hacks around this is to generate a pattern for the bubble display.
For example, data points with positive values can be colored, while negative-valued data points are left uncolored. Its size will now correspond to the equivalent positive value.
That is, the size of -10.5 will be 10.5, but uncolored.
Why Use Formplus To Collect Bubble Chart Data?
With the amount of data available today, the process of collecting relevant data for your Bubble Chart Data can be highly demanding. Therefore, you need a tool that will help you collect relevant data without doing any hard work.
Do you need a tool to help optimize your data collection process? Here are a few reasons why you should choose Formplus.
- Real-time updates: Receive real-time updates on your data without stress using Formplus. When you collect your Bubble Chart Data with Formplus surveys, you receive an email notification whenever a response has been added to your data.
The Google Sheet integration also ensures that your worksheet is updated immediately an entry is added to the dataset. You do not have to manually import the data into your worksheet each time there is an update.
Formplus automates this process for you each time, without fail.
- Security: Get rid of irrelevant responses on your surveys with the Captcha feature on Formplus. This feature prevents your form from being attacked by bots who leave spam messages.
Therefore, you will have little to no formatting to carry out on your generated Bubble chart data.
The data collected is also kept in secure cloud storage, away from third-parties. Formplus also supports Google Drive, Microsoft OneDrive, and Dropbox integration.
- Flexibility: You can use one of the existing Formplus survey templates or create your own from scratch using the Formplus builder. The builder offers you over 30+ form fields to use in collecting your data.
These form fields are capable of collecting any version of data, including images, documents, and even signatures. This feature is very applicable to job applications.
- Response Rate: Generate enough data for your bubble chart with an online survey that increases response rate. Some of these features include a save and resume feature, form validation, and the offline feature.
With form validation, you can eliminate no response biases from your survey. Respondents can also save their responses and resume whenever they please.
Formplus surveys can also be filled offline by respondents who stay in a remote area with an unstable internet connection.
- Generate Web Traffic: Generate more traffic to your website and social media pages with a submission button that links respondents to your website. Formplus allows you to add a link to your submission button in the form settings menu.
Disadvantages of Bubble Charts
- The circle sizes can make it difficult to ascertain specific values at a glance.
- It cannot be used to display a lot of data. The circles will overlap and the plot will become cluttered. Therefore, making the chart unreadable.
- It is almost impossible to determine the value of the third variable from the plot alone. This is because circle sizes cannot be visually measured. This can only be possible in instances where the bubbles are labeled with the sizes.
Conclusion
One of the common features of column charts and line charts is that they both have a numeric (y-axis) and categorical (x-axis) axis. But this is quite different from Bubble Graphs whose two axes are both numeric.
Just like Dot Plots, Bubble Charts can be said to be a variation of scatter plots but defined with 3 dimensions. The third dimension in the Bubble plot is a size indicator that determines the area of each bubble on the chart.
The dynamism of the bubble size is the distinguishing factor that makes it a popular visualization technique. With Bubble Chart, you can create a 3-dimensional plot in 2 dimensions.