## DESCRIPTION

This is an interface to the interpolation package present in the GNU Scientific Library.## SYNOPSIS

use PDL;

use PDL::GSL::INTERP;

my $x = sequence(10);

my $y = exp($x);

my $spl = PDL::GSL::INTERP->init('cspline',$x,$y);

my $res = $spl->eval(4.35);

$res = $spl->deriv(4.35);

$res = $spl->deriv2(4.35);

$res = $spl->integ(2.1,7.4);

## FUNCTIONS

*init()*

The init method initializes a new instance of INTERP. It needs as
input an interpolation type and two piddles holding the x and y
values to be interpolated. The GSL routines require that x be
monotonically increasing and a quicksort is performed by default to
ensure that. You can skip the quicksort by passing the option
{Sort => 0}.
The available interpolation types are :

- linear
- polynomial
- cspline (natural cubic spline)
- cspline_periodic (periodic cubic spline)
- akima (natural akima spline)
- akima_periodic (periodic akima spline)

Please check the GSL documentation for more information.

Usage:

$blessed_ref = PDL::GSL::INTERP->init($interp_method,$x,$y,$opt);

Example:

$x = sequence(10); $y = exp($x); $spl = PDL::GSL::INTERP->init('cspline',$x,$y) $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 1}) #same as above # no sorting done on x, user is certain that x is monotonically increasing $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 0});

*eval()*

The function eval returns the interpolating function at a given point. By default
it will barf if you try to extrapolate, to comply silently if the point to be
evaluated is out of range pass the option {Extrapolate => 1}
Usage:

$result = $spl->eval($points,$opt);

Example:

my $res = $spl->eval($x) $res = $spl->eval($x,{Extrapolate => 0}) #same as above # silently comply if $x is out of range $res = $spl->eval($x,{Extrapolate => 1})

*deriv()*

The deriv function returns the derivative of the
interpolating function at a given point. By default
it will barf if you try to extrapolate, to comply silently if the point to be
evaluated is out of range pass the option {Extrapolate => 1}
Usage:

$result = $spl->deriv($points,$opt);

Example:

my $res = $spl->deriv($x) $res = $spl->deriv($x,{Extrapolate => 0}) #same as above # silently comply if $x is out of range $res = $spl->deriv($x,{Extrapolate => 1})

*deriv2()*

The deriv2 function returns the second derivative
of the interpolating function at a given point. By default
it will barf if you try to extrapolate, to comply silently if the point to be
evaluated is out of range pass the option {Extrapolate => 1}
Usage:

$result = $spl->deriv2($points,$opt);

Example:

my $res = $spl->deriv2($x) $res = $spl->deriv2($x,{Extrapolate => 0}) #same as above # silently comply if $x is out of range $res = $spl->deriv2($x,{Extrapolate => 1})

*integ()*

The integ function returns the integral
of the interpolating function between two points.
By default it will barf if you try to extrapolate,
to comply silently if one of the integration limits
is out of range pass the option {Extrapolate => 1}
Usage:

$result = $spl->integ($a,$b,$opt);

Example:

my $res = $spl->integ($a,$b) $res = $spl->integ($a,$b,{Extrapolate => 0}) #same as above # silently comply if $a or $b are out of range $res = $spl->eval($a,$b,{Extrapolate => 1})

## BUGS

Feedback is welcome.## AUTHOR

This file copyright (C) 2003 Andres Jordan <[email protected]> All rights reserved. There is no warranty. You are allowed to redistribute this software/documentation under certain conditions. For details, see the file COPYING in the PDL distribution. If this file is separated from the PDL distribution, the copyright notice should be included in the file.The GSL interpolation module was written by Gerard Jungman.