So far, we've looked at line charts, bar charts, pie charts, and even charts used for the stock market. In this chapter, we will look at three other charts: the bubble chart and the block plot, which are similar to scatter plots, and the waterfall chart, which is a type of bar chart. In this chapter, we will:
- Discuss what a bubble chart is and the new data points we'll need to pass into our data arrays
- Create a bubble chart showing the revenue, units sold, and percentage of total profit
- Discuss how a block plot is similar to and different from a bubble chart
- Plot various product categories containing the revenue and units sold as data points
- Look at how waterfall charts visualize positive and negative data points
The next morning, we come in and try and catch up on tasks that were put on hold when the dashboard project came around. Around 10 o'clock, Sara stops by. "Morning, you two. So, I have a few more requests for you."
"In my department, we have been looking at our vendors. We are trying to figure out which ones are not performing as well. If some are underperforming, we want to cut them. With the newly released funds, we can try and work out better deals with our existing, better performing vendors."
Sara continues, "I'll leave the implementation up to you, but I want to look at the revenue and units sold for the TV manufacturers we sell. If we can then expand this out into computers and DVD players as well, that would be great. These categories have the highest margins for us."
Sara pauses for a moment, "I hate to rush you, but I need these charts for a presentation later this week. Can you use something instead of a bar chart or line graph?" We assure her we will find a solution.
Sara stands to leave. "I'll get the numbers together and send them over this afternoon." I ask her if she can send over the profit numbers as well. She agrees and heads back to her office.
We sit down to begin discussing what kind of chart we can use for Sara's project. I mention this project would be a good use for a bubble chart because it will allow us to plot a third data point.
Bubble charts use three data points. The first two points are plotted on the x and y axes like a normal line chart. However, the third point is plotted as the size of the bubble. Some charts create the bubble using the third point as the radius of the bubble, and others use it as the area. These differences can affect how charts are interpreted. Also, the simple fact of having a user trying to determine which circle is larger can be difficult. So, along with the visualization of the data with bubbles, it is also recommended to label the elements to aid understanding. We can see an example in the following screenshot:
Since each data series is independent of each other, bubble charts are considered a part of the scatterplot family. So, with Sara's chart, we can plot the total revenue for each manufacturer on the x axis, and the total units sold on the y axis. For the bubble size, we can pass in the percentage of profit generated by the manufacturer. This will give Sara a good indication of which manufacturers are performing well and which have the higher margins.