Question

Using ggplot2 for multifaceted diagram, the deciding variable on the number of rows or columns is

Answer 1

Ggplot2 is a package used for plotting which makes it simple to create complex plots from data in a data frame.  

It gives a programmatic interface for specifying which variables to plot and  how they are displayed and their visual properties.

Need of minimal changes if the underlying data change or if we decide to change from a bar plot.