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

       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.

perl v5.34.0                                       2022-02-08                                        INTERP(3pm)

       Feedback is welcome.

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

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.

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

       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 62 "INTERP.pm"

       PDL

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

          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);