mod_spline Module

Given arrays x(1:n) and y(1:n) containing a tabulated function, i.e., $y(i) = f(xi)$, with $x1<x2<\cdots<xN$ , and given values yp1 and ypn for the 1st derivative of the interpolating function at points 1 and n, respectively, this routine returns an array y2(1:n) of length n which contains the second derivatives of the interpolating function at the tabulated points xi. If yp1 and/or ypn are equal to 1.e30 or larger, the routine is signaled to set the corresponding boundary condition for a natural spline, with zero second derivative on that boundary. Parameter: NMAX is the largest anticipated value of n.