In 2013, EPA published final national recommended water quality criteria for the protection of aquatic life from the toxic effects of ammonia in freshwater.
These criteria are a function of water temperature and pH, so that the criteria concentration value changes with changing pH and temperature. Frequently the criteria values are plotted as a slice with one of the two variables held constant. But I wanted to see what the total criteria space looked like. One way to do this is with a 3D plot with the independent temperature and pH variables on the x and y axes (the horizontal plane) and the dependent Ammonia concentration on the z axis (vertical). Since shape of the surface is difficult to see from any one perspective, animation helps show the overall shape.
This plot was developed in R using plot3D and animation libraries.