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

BUGS

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

AUTHOR

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

90   diff_central
91         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
92
93       info not available
94
95       diff_central does not process bad values.  It will set the bad-value
96       flag of all output piddles if the flag is set for any of the input
97       piddles.
98
99   diff_backward
100         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
101
102       info not available
103
104       diff_backward does not process bad values.  It will set the bad-value
105       flag of all output piddles if the flag is set for any of the input
106       piddles.
107
108   diff_forward
109         Signature: (double x(); double [o] res(); double [o] abserr(); SV* funcion)
110
111       info not available
112
113       diff_forward does not process bad values.  It will set the bad-value
114       flag of all output piddles if the flag is set for any of the input
115       piddles.
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119perl v5.12.3                      2011-03-31                           DIFF(3)