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, ...

Four examples illustrate how one might use these routines: interpolation by splines of general order k (and not necessarily at the knots); least squares approximation by splines to discrete data; the ...

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