RKStages[rk]
returns the number of stages of rk.
The number of stages for the classical fourth order Runge–Kutta method:
RK RKA RKB RKC
![A in TemplateBox[{}, Reals]^(sxs)](Files/RKStages.en/2.png "A in TemplateBox[{}, Reals]^(sxs)"){kind=small}
![b in TemplateBox[{}, Reals]^s](Files/RKStages.en/3.png "b in TemplateBox[{}, Reals]^s"){kind=small}
![c in TemplateBox[{}, Reals]^s](Files/RKStages.en/4.png "c in TemplateBox[{}, Reals]^s"){kind=small}