def vector_from_points_xy(a, b):
    """
    Create a vector based on a start point a and end point b in the XY-plane.

    Parameters
    ----------
    a : sequence of float
        XY(Z) coordinates of a 2D or 3D point (Z will be ignored).
    b : sequence of float
        XY(Z) coordinates of a 2D or 3D point (Z will be ignored).

    Returns
    -------
    ab : tuple
        Resulting 3D vector in the XY-plane (Z = 0.0).

    Notes
    -----
    The result of this function is equal to ``subtract_vectors(b, a)``

    """
    return b[0] - a[0], b[1] - a[1], 0.0
