Simple demo, refreshed from years in the safe.
Offers 3 types ODE solvers ... experiment more
from the 17 Smath built in library.
Comments welcome ... Jean.

ODE RK4 INTERpolate sol(x) Copy.sm (34 KiB) downloaded 73 time(s).

... as well, you can interpolate in-situ
the spiral closed contour [bi-direction 'x'].

ODE rkfixed SPIRAL.sm (35 KiB) downloaded 64 time(s).