ggmatplot - Plot Columns of Two Matrices Against Each Other Using 'ggplot2'

A quick and easy way of plotting the columns of two matrices or data frames against each other using 'ggplot2'. Although 'ggmatplot' doesn't provide the same flexibility as 'ggplot2', it can be used as a workaround for having to wrangle wide format data into long format for plotting with 'ggplot2'.