The idea behind visualizing data is to transfer the information in the right form and use the correct medium. We often observe the use of two different pie charts placed adjacent to each other. These plots are used to compare data between two different time periods. Schwabish (2014) provides slope charts and bar plots as alternatives to using two separate pie charts. The slope charts can be used to study the correlation between variables or to study the change in the same variable between two different time periods.
Some of the applications of slope charts are as follows:
Changing obesity rates in the United States
Changes in Child Mortality Rate
Cancer Survival
The following slope chart implementation has been inspired by the New York Times child mortality infographic: