PDL::GSL::INTERP (3)

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NAME

PDL::GSL::INTERP - PDL interface to Interpolation routines in GSL

DESCRIPTION

This is an interface to the interpolation package present in the 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 It needs as input an interpolation type and two piddles holding the x and y values to be interpolated. The 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

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.

SEE ALSO

The

documentation is online at

  www.gnu.org/software/gsl/manual

AUTHOR

This file copyright (C) 2003 Andres Jordan <andresj@physics.rutgers.edu> All rights reserved. There is no warranty. You are allowed to redistribute this software/documentation under certain conditions. For details, see the file in the distribution. If this file is separated from the distribution, the copyright notice should be included in the file.

The

interpolation module was written by Gerard Jungman.