gx = np.array([[1, 0, -1], [2, 0, -2], [1, 0, -1]])
gy = np.array([[1, 2, 1], [0, 0, 0], [-1, -2, -1]])

def create_vector(image):
    """Creates a gradient vector for each pixel in the image
    Returns: vec_data: [mag, angle, avg_value]"""
Vectorizing non-trivial for loop in numpy