Manual Reference Pages - 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
CONTENTS
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
| splift (3) | March 11, 2021 |
