Compute trajectories
Computes trajectories of particles in a time-varying velocity field.
Trajectory(formula, x0, y0, cyclical = FALSE, data = NULL, res = 2)
formula: a formula indicating dependent and independent variables in the form of dx + dy ~ x + y + t.x0, y0: starting coordinates of the particles.cyclical: logical vector of boundary condition for x and y.data: optional data.frame containing the variables.res: resolution parameter (higher numbers increases the resolution)