NAME

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

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.

SEE ALSO

       PDL

       The GSL documentation is online at

         http://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 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.