Function quad

lib/matplotlib/tests/test_triangulation.py:475–476

(x, y)

    (a, b, c) = (1.23, -4.79, 0.6)

    def quad(x, y):
        return a*(x-0.5)**2 + b*(y-0.5)**2 + c*x*y

    def gradient_quad(x, y):
        return (2*a*(x-0.5) + c*y, 2*b*(y-0.5) + c*x)