Bubble plots help us to visualize three or four dimensions of data. Each datum in a bubble plot consists not only of two values used to plot against the X and Y axes, but also one or two additional values which are commonly represented by different size symbols and/or colors.

To demonstrate a bubble plot, the following image shows the result of our example:

The data behind this chart is a data set that was pulled together from three different datasets from the World Bank. This data correlates life expectancy at birth relative to the fertility rate for all the countries in the World Bank data for the year 2013.

This chart plots age along the X axis and the birth rate along the Y axis. The relative population of a country is represented by the size of the circle, and the color of the circle represents the economic region of the country as categorized by the World Bank.

We won't dive deeply into this data. It is available at https://goo.gl/K3yuuy.

The first few lines of the...