VectorField
Creates a planar vector field plot.
Syntax

VectorField(f, ❨xmin, xmax[, δx]❩, ❨ymin, ymax[, δy]❩)

f
is a function D → ℝ² where D ⊂ ℝ² 
xmin
,xmax
,ymin
, andymax
are real numbers 
δx
andδy
are nonnegative real numbers

Description
The VectorField
function creates a plot of the vector field f
in the rectangular region [xmin, xmax] × [ymin, ymax]
with a sampling distance of δx
in the first dimension and δy
in the second dimension. The sampling distance is the distance between arrows. If omitted, a reasonable default value is used (typically producing a plot with about 20 arrows along each direction).
The plot is shown in the current diagram and a reference to the plot is returned.
Examples
D ≔ diagram("vector field"); sf ≔ heatmap((x, y) ↦ x^2 + y^2, ❨−10, 10❩, ❨−10, 10❩, '("white", "red")); vf ≔ VectorField((x, y) ↦ ❨2⋅x, 2⋅y❩, ❨−10, 10❩, ❨−10, 10❩)