ond
    to the inverse of the standard-deviation of the errors in z,
    then a good s-value should be found in the range
    ``(m-sqrt(2*m),m+sqrt(2*m))`` where m=len(x).
eps : float, optional
    A threshold for determining the effective rank of an
    over-determined linear system of equations (0 < eps < 1).
    `eps` is not likely to need changing.
tx, ty : ndarray, optional
    Rank-1 arrays of the knots of the spline for task=-1
full_output : int, optional
    Non-zero to return optional outputs.
nxest, nyest : int, optional
    Over-estimates of the total number of knots. If None then
    ``nxest = max(kx+sqrt(m/2),2*kx+3)``,
    ``nyest = max(ky+sqrt(m/2),2*ky+3)``.
quiet : int, optional
    Non-zero to suppress printing of messages.

Returns
-------
tck : array_like
    A list [tx, ty, c, kx, ky] containing the knots (tx, ty) and
    coefficients (c) of the bivariate B-spline representation of the
    surface along with the degree of the spline.
fp : ndarray
    The weighted sum of squared residuals of the spline approximation.
ier : int
    An integer flag about splrep success. Success is indicated if
    ier<=0. If ier in [1,2,3] an error occurred but was not raised.
    Otherwise an error is raised.
msg : str
    A message corresponding to the integer flag, ier.

See Also
--------
splprep, splrep, splint, sproot, splev
UnivariateSpline, BivariateSpline

Notes
-----
See `bisplev` to evaluate the value of the B-spline given its tck
representation.

If the input data is such that input dimensions have incommensurate
units and differ by many orders of magnitude, the interpolant may have
numerical artifacts. Consider rescaling the data before interpolation.

References
----------
.. [1] Dierckx P.:An algorithm for surface fitting with spline functions
   Ima J. Numer. Anal. 1 (1981) 267-283.
.. [2] Dierckx P.:An algorithm for surface fitting with spline functions
   report tw50, Dept. Computer Science,K.U.Leuven, 1980.
.. [3] Dierckx P.:Curve and surface fitting with splines, Monographs on
   Numerical Analysis, Oxford University Press, 1993.

Examples
--------
Examples are given :ref:`in the tutorial <tutorial-interpolate_2d_spline>`.

z!len(x)==len(y)==len(z) must hold.Nr`