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);

NOMENCLATURE

       Throughout this documentation we strive to use the same variables that are present in the
       original GSL documentation (see See Also). Oftentimes those variables are called "a" and
       "b". Since good Perl coding practices discourage the use of Perl variables $a and $b, here
       we refer to Parameters "a" and "b" as $pa and $pb, respectively, and Limits (of domain or
       integration) as $la and $lb.  #line 63 "INTERP.pm"

FUNCTIONS

   init
         Signature: (double x(n); double y(n); gsl_spline *spl)

       The init method initializes a new instance of INTERP. It needs as input an interpolation
       type and two ndarrays 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});

       init does not process bad values.  It will set the bad-value flag of all output ndarrays
       if the flag is set for any of the input ndarrays.

   eval
         Signature: (double x(); double [o] out(); gsl_spline *spl;gsl_interp_accel *acc)

       The function eval returns the interpolating function at a given point.  It will barf with
       an "input domain error" if you try to extrapolate.

       Usage:

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

       Example:

           my $res = $spl->eval($x)

       eval processes bad values.  It will set the bad-value flag of all output ndarrays if the
       flag is set for any of the input ndarrays.

   deriv
         Signature: (double x(); double [o] out(); gsl_spline *spl;gsl_interp_accel *acc)

       The deriv function returns the derivative of the interpolating function at a given point.
       It will barf with an "input domain error" if you try to extrapolate.

       Usage:

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

       Example:

           my $res = $spl->deriv($x)

       deriv does not process bad values.  It will set the bad-value flag of all output ndarrays
       if the flag is set for any of the input ndarrays.

   deriv2
         Signature: (double x(); double [o] out(); gsl_spline *spl;gsl_interp_accel *acc)

       The deriv2 function returns the second derivative of the interpolating function at a given
       point.  It will barf with an "input domain error" if you try to extrapolate.

       Usage:

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

       Example:

           my $res = $spl->deriv2($x)

       deriv2 does not process bad values.  It will set the bad-value flag of all output ndarrays
       if the flag is set for any of the input ndarrays.

   integ
         Signature: (double a(); double b(); double [o] out(); gsl_spline *spl;gsl_interp_accel *acc)

       The integ function returns the integral of the interpolating function between two points.
       It will barf with an "input domain error" if you try to extrapolate.

       Usage:

           $result = $spl->integ($la,$lb);

       Example:

           my $res = $spl->integ($la,$lb)

       integ does not process bad values.  It will set the bad-value flag of all output ndarrays
       if the flag is set for any of the input ndarrays.

BUGS

       Feedback is welcome.

SEE ALSO

       PDL

       The GSL documentation for interpolation is online at
       <https://www.gnu.org/software/gsl/doc/html/interp.html>

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.