What is Bubble Chart?

It is an extension of the scatter plot with data points being replaced with bubbles. A bubble chart is a better choice when input data has three or more series, each contains a set of values. 

Typically, the bubble charts depict the values of three numeric variables, but there can be more of them. Each bubble stands for a single data point, and the values for each bubble can be depicted by:

• its horizontal position on the x-axis
• its vertical position on the y-axis
• its size

When there are more than three variables, it can be depicted also by:

• its color
• its movement when the chart is animated

The bubble chart issue

Bubble charts, although great at facilitating the understanding of complex social, economic, or medical relationships, can be challenging: if there are too many bubbles; this format becomes hard to read. Also, the static bubble charts are good for visualizing situations and correlations but fail when explaining the reason and the way on how it occurred.