Process points with PROC G3GRID. PARTIAL specifies that a spline be used to estimate the derivatives for the biquintic polynomial interpolation. NEAR= specifies the number of nearest neighbors to be used for computing the estimates of the first and second derivatives. 
proc g3grid data=reflib.nums out=partial;
   grid y*x=z / partial
                near=8
                axis1=-5 to 5 by .5
                axis2=-5 to 5 by .5;
run;