I am a control engineering student and I would like to create a state space model of a given real world problem. The idea is to consider something that can be experienced in the real world, for example, the cultivation of wheat every year, or something of this kind.
I would like to model such types of problems using a state space model of the form
$$\dot{x}=Ax+Bu$$
or, in the nonlinear case, using
$$\dot{x}=f(x)+g(x)u$$
How can I do such modeling?