def y_domain_spline(spline_function, x_domain_spline):
    """
    Calculate a y domain based on a function.

    Parameters
    ----------
    spline_function : function
        The spline function.
    x_domain_spline : ndarray
        The (n, 1)-shaped ndarray.

    Returns
    -------
    ndarray
        The spline_function(x_domain_spline) vector.
    """
    return spline_function(x_domain_spline)
