C Library Functions - splift (3)

NAME

splift(3f) - [M_math:fit] fits a spline to the n data points given in x and y and also returns first and second derivatives

Synopsis
Description
Options
Returns
Example
Pedigree

SYNOPSIS

subroutine splift(x,y,yp,ypp,n,ierr,a1,b1,an,bn)

   real,intent(in)            :: x(n),y(n)
   real,intent(out)           :: yp(n),ypp(n)
   integer,intent(in)         :: n
   integer,intent(out)        :: ierr
   real,intent(in)            :: a1
   real,intent(in)            :: b1
   real,intent(in)            :: an
   real,intent(in)            :: bn

DESCRIPTION

SPLIFT(3f) fits a spline to the N data points given in X and Y and returns the first and second derivatives in YP and YPP. The resulting spline, defined by the arrays X, Y, and YPP, may then be interpolated (if desired) using SPLINT(3f).
For a smoothing spline fit see SUBROUTINE SMOOTH.

OPTIONS

X array of abscissas (in increasing order)

Y array of ordinates

N number of data points (the dimension of X,Y,YP and YPP)

A1,B1,AN,BN
end condition specifications
                    The end conditions of the spline are
                         YPP(1) = A1*YPP(2) + B1
                    and
                         YPP(N) = AN*YPP(N-1) + BN,
                    where
                         ABS(A1).LT.1.0 and ABS(AN).LT.1.0.
The smoothest (i.e., least integral of square of second derivative) spline is obtained by A1=B1=AN=BN=0. If extrapolation outside the range from X(1) to X(N) is to be done (By SPLINT(3f), say), better results may be obtained by using A1=AN=0.5, B1=BN=0.

RETURNS

YP Resulting derivative

YPP Resulting second derivative

IERR Error status.

NORMAL CODES

=0 means the requested spline was computed.

ABNORMAL CODES

=1 means N was too small (.LT.4).

=2 means the abscissas were not strictly increasing.

EXAMPLE

PEDIGREE

Original written by:

Rondall E. Jones Sandia Mathematical Program Library Applied Mathematics Division 2642 Sandia Laboratories P. O. Box 5800 Albuquerque, New Mexico 87115 Control Data 6600 Version 5.1, 10 December 1973

WARD implementation S. J. Orbon 4/1/1974

F90+ Implementation J. S. Urban

Nemo Release 3.1

splift (3)

February 23, 2025

Generated by manServer 1.08 from 6a5dff24-346d-457e-911b-3b9d8b0b380b using man macros.

X	array of abscissas (in increasing order)
Y	array of ordinates
N	number of data points (the dimension of X,Y,YP and YPP)
A1,B1,AN,BN
	end condition specifications

YP	Resulting derivative
YPP	Resulting second derivative
IERR	Error status.

=1	means N was too small (.LT.4).
=2	means the abscissas were not strictly increasing.