def gaussian_variogram_model(m, d):
    """Gaussian model, m is [psill, range, nugget]"""
    psill = float(m[0])
    range_ = float(m[1])
    nugget = float(m[2])
    return psill * (1. - np.exp(-d**2./(range_*4./7.)**2.)) + nugget
Gaussian model, m is [psill, range, nugget]