1019.sagews

x, y =var('x y')
plot_vector_field([-y, x], (x,-2, 2), (y,-2, 2))

x, y, z = var('x y z')
f(x,y)=1/(x^2+y^2)^(3/2)
plot_vector_field(f.gradient(), (x, -2, 2), (y, -2, 2))