Not at all. Coefficient fitting is when you know what output you want, and you have a lot of inputs, and you have some idea of the functional form. In this ca

Not at all. Coefficient fitting is when you know what output you want, and you have a lot of inputs, and you have some idea of the functional form. In this case, they didn't say "I want to predict the position of the pendulum based on time given these initial conditions." They just said "here is a bunch of data" and it came back with useful equations.