PDL::GSL::DIFF (3)

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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 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

diff_central

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

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* function)

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* function)

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.

gsldiff

This functions serves as an interface to the three differentiation functions present in 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

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 bug database (the database is always linked from <pdl.perl.org>).

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

differentiation routines were written by David Morrison.