Drawing a bubble plot

Until now, we saw how we can work points' shapes and colors to display more information, but what about sizes? Sizes are also a feasible option. Plots that combine circles with sizes to transmit information are known as bubble plots. This recipe's intention is to brew the working material for the following recipes; to do this, we will craft and store a bubble plot.

For now, a little context. By the end of the 16th century, Spain had this navy that was called "La Feliscima Armada". Here, we are analyzing the relation between soldiers, sailors, and ships held by each navy fleet. What are you expecting?  Will the fleet with more sailors be the fleet with more ships? Let's call ggplot2 to solve this question by drawing a bubble plot on this query.

Getting ready

The dataset we are about to use is called Armada and comes from the HistData package, so we better check the last one:

> if( !require(HistData)){ install.packages('HistData')}

The Armada data frame has 10 observations...