It would be unwise to ignore the trajectory, a.k.a. rate of change. In general, when looking at some phenomena, don't only look at the primary measurement (e.g

It would be unwise to ignore the trajectory, a.k.a. rate of change. In general, when looking at some phenomena, don't only look at the primary measurement (e.g. f(x)). It is often useful to look at the derivative (e.g. df/dx) as well. P.S. The second derivative also may be informative as well. Keep going if you want.