Geom.vectorfield

Draw a vectorfield of a 2D function or a matrix. A vectorfield consists of gradient vectors calculated for particular points in a space.

Aesthetics

z: 2D function or a matrix that represent "heights" relative to to the x-y plane.
x (optional): Vector of X-coordinates. If z is a matrix, then the length of x must be equal to the number of rows in z.
y (optional): Vector of Y-coordinates. If z is a matrix, then the length of y must be equal to the number of columns in z.

Arguments

smoothness (optional): Sets the smoothness of the vectorfield, defaults to 1.0. Smaller values (→0) result in more local smoothing. Larger values (→∞) will approach a plane of best fit.
scale (optional): Sets the size of vectors, defaults to 1.0.
samples (optional): Sets the size of the grid at which to estimate vectors, defaults to 20 (i.e. grid is 20 x 20). See the first example below.

Examples

coord = Coord.cartesian(xmin=-2, xmax=2, ymin=-2, ymax=2)
plot(coord, z=(x,y)->x*exp(-(x^2+y^2)),
        xmin=[-2], xmax=[2], ymin=[-2], ymax=[2],
# or:     x=-2:0.25:2.0, y=-2:0.25:2.0,
        Geom.vectorfield(scale=0.4, samples=17), Geom.contour(levels=6),
        Scale.x_continuous(minvalue=-2.0, maxvalue=2.0),
        Scale.y_continuous(minvalue=-2.0, maxvalue=2.0),
        Guide.xlabel("x"), Guide.ylabel("y"), Guide.colorkey("z")
    )

volcano = Matrix{Float64}(dataset("datasets", "volcano"))
volc = volcano[1:4:end, 1:4:end]
coord = Coord.cartesian(xmin=1, xmax=22, ymin=1, ymax=16)
plot(coord, z=volc, x=1.0:22, y=1.0:16,
        Geom.vectorfield(scale=0.05), Geom.contour(levels=7),
        Scale.x_continuous(minvalue=1.0, maxvalue=22.0),
        Scale.y_continuous(minvalue=1.0, maxvalue=16.0),
        Guide.xlabel("x"), Guide.ylabel("y"),
        Theme(key_position=:none)
    )