1INTERP(3)             User Contributed Perl Documentation            INTERP(3)
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4

NAME

6       PDL::GSL::INTERP - PDL interface to Interpolation routines in GSL
7

DESCRIPTION

9       This is an interface to the interpolation package present in the GNU
10       Scientific Library.
11

SYNOPSIS

13          use PDL;
14          use PDL::GSL::INTERP;
15
16          my $x = sequence(10);
17          my $y = exp($x);
18
19          my $spl = PDL::GSL::INTERP->init('cspline',$x,$y);
20
21          my $res = $spl->eval(4.35);
22          $res = $spl->deriv(4.35);
23          $res = $spl->deriv2(4.35);
24          $res = $spl->integ(2.1,7.4);
25

NOMENCLATURE

27       Throughout this documentation we strive to use the same variables that
28       are present in the original GSL documentation (see See Also).
29       Oftentimes those variables are called "a" and "b". Since good Perl
30       coding practices discourage the use of Perl variables $a and $b, here
31       we refer to Parameters "a" and "b" as $pa and $pb, respectively, and
32       Limits (of domain or integration) as $la and $lb.
33

FUNCTIONS

35   init()
36       The init method initializes a new instance of INTERP. It needs as input
37       an interpolation type and two piddles holding the x and y values to be
38       interpolated. The GSL routines require that x be monotonically
39       increasing and a quicksort is performed by default to ensure that. You
40       can skip the quicksort by passing the option {Sort => 0}.
41
42       The available interpolation types are :
43
44       linear
45       polynomial
46       cspline (natural cubic spline)
47       cspline_periodic  (periodic cubic spline)
48       akima (natural akima spline)
49       akima_periodic  (periodic akima spline)
50
51       Please check the GSL documentation for more information.
52
53       Usage:
54
55           $blessed_ref = PDL::GSL::INTERP->init($interp_method,$x,$y,$opt);
56
57       Example:
58
59           $x = sequence(10);
60           $y = exp($x);
61
62           $spl = PDL::GSL::INTERP->init('cspline',$x,$y)
63           $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 1}) #same as above
64
65           # no sorting done on x, user is certain that x is monotonically increasing
66           $spl = PDL::GSL::INTERP->init('cspline',$x,$y,{Sort => 0});
67
68   eval()
69       The function eval returns the interpolating function at a given point.
70       It will barf with an "input domain error" if you try to extrapolate.
71
72       Usage:
73
74           $result = $spl->eval($points);
75
76       Example:
77
78           my $res = $spl->eval($x)
79
80   deriv()
81       The deriv function returns the derivative of the interpolating function
82       at a given point.  It will barf with an "input domain error" if you try
83       to extrapolate.
84
85       Usage:
86
87           $result = $spl->deriv($points);
88
89       Example:
90
91           my $res = $spl->deriv($x)
92
93   deriv2()
94       The deriv2 function returns the second derivative of the interpolating
95       function at a given point.  It will barf with an "input domain error"
96       if you try to extrapolate.
97
98       Usage:
99
100           $result = $spl->deriv2($points);
101
102       Example:
103
104           my $res = $spl->deriv2($x)
105
106   integ()
107       The integ function returns the integral of the interpolating function
108       between two points.  It will barf with an "input domain error" if you
109       try to extrapolate.
110
111       Usage:
112
113           $result = $spl->integ($la,$lb);
114
115       Example:
116
117           my $res = $spl->integ($la,$lb)
118

BUGS

120       Feedback is welcome.
121

SEE ALSO

123       PDL
124
125       The GSL documentation for interpolation is online at
126       <https://www.gnu.org/software/gsl/doc/html/interp.html>
127

AUTHOR

129       This file copyright (C) 2003 Andres Jordan
130       <andresj@physics.rutgers.edu> All rights reserved. There is no
131       warranty. You are allowed to redistribute this software/documentation
132       under certain conditions. For details, see the file COPYING in the PDL
133       distribution. If this file is separated from the PDL distribution, the
134       copyright notice should be included in the file.
135
136       The GSL interpolation module was written by Gerard Jungman.
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140perl v5.32.1                      2021-02-15                         INTERP(3)
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