PDL::GSL::DIFF(3pm)

1DIFF(3)               User Contributed Perl Documentation              DIFF(3)
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NAME

6       PDL::GSL::DIFF - PDL interface to numerical differentiation routines in
7       GSL
8

DESCRIPTION

10       This is an interface to the numerical differentiation package present
11       in the GNU Scientific Library.
12

SYNOPSIS

14          use PDL;
15          use PDL::GSL::DIFF;
16
17          my $x0 = 3.3;
18
19          my @res = gsldiff(\&myfunction,$x0);
20          # same as above:
21          @res = gsldiff(\&myfunction,$x0,{Method => 'central'});
22
23          # use only values greater than $x0 to get the derivative
24          @res =  gsldiff(\&myfunction,$x0,{Method => 'forward'});
25
26          # use only values smaller than $x0 to get the derivative
27          @res = gsldiff(\&myfunction,$x0,{Method => 'backward'});
28
29          sub myfunction{
30            my ($x) = @_;
31            return $x**2;
32          }
33

FUNCTIONS

35       gsldiff()
36
37       This functions serves as an interface to the three differentiation
38       functions present in GSL: gsl_diff_central, gsl_diff_backward and
39       gsl_diff_forward. To compute the derivative, the central method uses
40       values greater and smaller than the point at which the derivative is to
41       be evaluated, while backward and forward use only values smaller and
42       greater respectively. gsldiff() returns both the derivative and an
43       absolute error estimate. The default  method is 'central', others can
44       be specified by passing an option.
45
46       Please check the GSL documentation for more information.
47
48       Usage:
49
50         ($d,$abserr) = gsldiff($function_ref,$x,{Method => $method});
51
52       Example:
53
54         #derivative using default method ('central')
55         ($d,$abserr) = gsldiff(\&myf,3.3);
56
57         #same as above with method set explicitly
58         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'central'});
59
60         #using backward & forward methods
61         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'backward'});
62         ($d,$abserr) = gsldiff(\&myf,3.3,{Method => 'forward'});
63
64         sub myf{
65           my ($x) = @_;
66           return exp($x);
67         }
68

BUGS

70       Feedback is welcome. Log bugs in the PDL bug database (the database is
71       always linked from http://pdl.perl.org).
72

AUTHOR

81       This file copyright (C) 2003 Andres Jordan <andresj@physics.rut‐
82       gers.edu> All rights reserved. There is no warranty. You are allowed to
83       redistribute this software documentation under certain conditions. For
84       details, see the file COPYING in the PDL distribution. If this file is
85       separated from the PDL distribution, the copyright notice should be
86       included in the file.
87
88       The GSL differentiation routines were written by David Morrison.
89

FUNCTIONS

91       diff_central
92
93         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
94
95       info not available
96
97       diff_backward
98
99         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
100
101       info not available
102
103       diff_forward
104
105         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
106
107       info not available
108
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111perl v5.8.8                       2006-12-02                           DIFF(3)