NAME

       PDL::GSL::DIFF - PDL interface to numerical differentiation routines in GSL

DESCRIPTION

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

SYNOPSIS

          use PDL;
          use PDL::GSL::DIFF;

          my $x0 = 3.3;

          my @res = gsldiff(\&myfunction,$x0);
          # same as above:
          @res = gsldiff(\&myfunction,$x0,{Method => 'central'});

          # use only values greater than $x0 to get the derivative
          @res =  gsldiff(\&myfunction,$x0,{Method => 'forward'});

          # use only values smaller than $x0 to get the derivative
          @res = gsldiff(\&myfunction,$x0,{Method => 'backward'});

          sub myfunction{
            my ($x) = @_;
            return $x**2;
          }

FUNCTIONS

   gsldiff()
       This functions serves as an interface to the three differentiation functions present in GSL:
       gsl_diff_central, gsl_diff_backward and gsl_diff_forward. To compute the derivative, the central method
       uses values greater and smaller than the point at which the derivative is to be evaluated, while backward
       and forward use only values smaller and greater respectively. gsldiff() returns both the derivative and
       an absolute error estimate. The default  method is 'central', others can be specified by passing an
       option.

       Please check the GSL documentation for more information.

       Usage:

         ($d,$abserr) = gsldiff($function_ref,$x,{Method => $method});

       Example:

         #derivative using default method ('central')
         ($d,$abserr) = gsldiff(\&myf,3.3);

         #same as above with method set explicitly
         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'central'});

         #using backward & forward methods
         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'backward'});
         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'forward'});

         sub myf{
           my ($x) = @_;
           return exp($x);
         }

BUGS

       Feedback is welcome. Log bugs in the PDL bug database (the database is always linked from
       <http://pdl.perl.org>).

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 differentiation routines were written by David Morrison.

FUNCTIONS

   diff_central
         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)

       info not available

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

   diff_backward
         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)

       info not available

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

   diff_forward
         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)

       info not available

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