This example then specifies a smoothed spline interpolation method on the GRID statement. As shown by the following output, the resulting surface plot is smoother still.

This example specifies a partial spline interpolation method on the GRID statement, using eight nearest neighbors for computing the estimates of the first and second derivatives. The output data set, ...

Although univariate spline functions play a major role in their construction, these bivariate interpolation functions are not tensor product splines. Indeed, the function space associated with this ...

Robert Hummel, Sampling for Spline Reconstruction, SIAM Journal on Applied Mathematics, Vol. 43, No. 2 (Apr., 1983), pp. 278-288 ...