Some of the projects have really transformative methods of turning one set of data (i.e. borrow direct data) into another set of seemingly unrelated data (environmental impact of borrow direct). It is often a good idea to show these calculations in your visualization, because the innovation is part of the charm of the visualization.
So how exactly do you put mathematical calculations in visualizations without seeming too wordy and complex? Here are some examples from Jessica Xu, an alum of the class and math visualization extraordinaire from 2014.