#### Example

Input:

plotfield(4*sin(t*y),[t=0..2,y=-3..7])

Output:

To draw a vector field:

- plotfield takes two mandatory arguments and two optional arguments:
  - V, a list of two expressions involving two variables.
  - vars, a list of the two variables. The variables can optionally include their ranges var=a..b.
  - Optionally, xstep=n to specify the discretization of the first variable.
  - Optionally, ystep=m to specify the discretization of the second variable.
- plotfield(V,vars ⟨ ,xstep=n,ystep=m⟩) draws the vector field given by V.

#### Example

Input:

plotfield(5*[-y,x],[x=-1..1,y=-1..1])

Output: