def METHOD_NAME(self):
    """ Returns interpolator to interpolate results as a function of speed and altitude """
    from scipy.interpolate import LinearNDInterpolator, interp1d
    import numpy as np
    alts = np.unique(self.Alt)
    if len(alts) > 1:
        return LinearNDInterpolator((self.Vinf, self.Alt), (self.CD_Total))
    else:
        intrp = interp1d(self.Vinf, self.CD_Total)
        return lambda v, a: intrp(v)