'The y direction of the ray.
Positive infinity if the ray points in the positive y direction,
negative infinity if the ray points in the negative y direction,
or 0 if the ray is horizontal.
See Also
xdirection
Examples
>>> from sympy import Point, Ray
>>> p1, p2, p3 = Point(0, 0), Point(-1, -1), Point(-1, 0)
>>> r1, r2 = Ray(p1, p2), Ray(p1, p3)
>>> r1.ydirection
-oo
>>> r2.ydirection
0'

@property
def ydirection(self):

    if (self.p1.y < self.p2.y):
        return S.Infinity
    elif (self.p1.y == self.p2.y):
        return S.Zero
    else:
        return S.NegativeInfinity
