Math::Spline(3pm)

1Spline(3)             User Contributed Perl Documentation            Spline(3)
2
3
4

SYNOPSIS

6           require Math::Spline;
7           $spline=new Math::Spline(\@x,\@y)
8           $y_interp=$spline->evaluate($x);
9
10           use Math::Spline qw(spline linsearch binsearch);
11           use Math::Derivative qw(Derivative2);
12           @y2=Derivative2(\@x,\@y);
13           $index=binsearch(\@x,$x);
14           $index=linsearch(\@x,$x,$index);
15           $y_interp=spline(\@x,\@y,\@y2,$index,$x);
16

DESCRIPTION

18       This package provides cubic spline interpolation of numeric data. The
19       data is passed as references to two arrays containing the x and y ordi‐
20       nates. It may be used as an exporter of the numerical functions or,
21       more easily as a class module.
22
23       The Math::Spline class constructor new takes references to the arrays
24       of x and y ordinates of the data. An interpolation is performed using
25       the evaluate method, which, when given an x ordinate returns the inter‐
26       polate y ordinate at that value.
27
28       The spline function takes as arguments references to the x and y ordi‐
29       nate array, a reference to the 2nd derivatives (calculated using Deriv‐
30       ative2, the low index of the interval in which to interpolate and the x
31       ordinate in that interval. Returned is the interpolated y ordinate. Two
32       functions are provided to look up the appropriate index in the array of
33       x data. For random calls binsearch can be used - give a reference to
34       the x ordinates and the x loopup value it returns the low index of the
35       interval in the data in which the value lies. Where the lookups are
36       strictly in ascending sequence (e.g. if interpolating to produce a
37       higher resolution data set to draw a curve) the linsearch function may
38       more efficiently be used. It performs like binsearch, but requires a
39       third argument being the previous index value, which is incremented if
40       necessary.
41

NOTE

43       requires Math::Derivative module
44

EXAMPLE

46           require Math::Spline;
47           my @x=(1,3,8,10);
48           my @y=(1,2,3,4);
49           $spline=new Math::Spline(\@x,\@y);
50           print $spline->evaluate(5)."\n";
51
52       produces the output
53
54       2.44
55

HISTORY

57       $Log: Spline.pm,v $ Revision 1.1  1995/12/26 17:28:17  willijar Initial
58       revision
59

BUGS

61       Bug reports or constructive comments are welcome.
62

AUTHOR

64       John A.R. Williams <J.A.R.Williams@aston.ac.uk>
65