NAME

Math::Interpolator::Source - source of points for use in interpolation

SYNOPSIS

        use Math::Interpolator::Source;

        $pt = Math::Interpolator::Source->new(sub { ... }, $x);
        $pt = Math::Interpolator::Source->new(sub { ... }, $x, $y);

        $x = $pt->x;
        $y = $pt->y;

        $role = $pt->role;

        $points = $pt->expand;

DESCRIPTION

An object of this type represents a potential to generate some number of adjacent knots on a one-dimensional curve. It is intended for use with Math::Interpolator, which will interpolate a curve between knots. A source is expanded into knots only if required for an attempted interpolation.

For interpolation in a particular part of a curve, a number of known knots are required, each one consisting of an x/y coordinate pair. It is not necessary to know all knot coordinates, or even the number of knots, elsewhere on the curve. A source stands in for a group of knots that has not yet been examined in detail.

A source covers a contiguous range of x coordinates. It is not necessary to know precisely what that range is; the whole range is represented by a single x coordinate that lies within it. When that range of x coordinates needs to be examined, the source is expanded, replacing it with the entire group of knots that lies within the range. If reverse interpolation is to be performed then the same goes for y coordinates too.

The expansion of a source may include more sources for subranges.

CONSTRUCTOR

Math::Interpolator::Source->new(EXPANDER, X[, Y])

Creates and returns a new source object. EXPANDER must be a reference to a function, which will be called to implement the expand method.

A representative x coordinate must be supplied which is within the range of x coordinates that is covered by the source. It is not required for the x coordinate to match any of the knots that will be generated, nor even for it to be between generated knots.

If x values are to be interpolated as well as y values, then a representative y coordinate must also be supplied. This works in exactly the same way as the representative x coordinate. If interpolation is only to be performed in one direction then a y coordinate is not required.

METHODS

$pt->x

Returns the representative x coordinate of the source.

$pt->y

Returns the representative y coordinate of the source, if there is one. dies if not.

$pt->role

Returns the string "SOURCE". This is used to distinguish sources from other types of entity that could appear in an interpolator's point list.

$pt->expand

Returns a reference to an array of point objects represented by this source. The types of objects permitted to be returned are the same as permitted when constructing an interpolator: knots and sources. The array may be empty. If non-empty, the resulting points are sorted in monotonically non-decreasing order of x coordinates.

dies if expansion is presently impossible.

SUBCLASSING

The interpolator uses only this public interface, so it is acceptable to substitute any other class that implements this interface. This may be done by subclassing this class, or by reimplementing all four methods independently. This is useful, for example, to avoid having to package all the data necessary for expansion into a closure.

SEE ALSO

Math::Interpolator, Math::Interpolator::Knot

AUTHOR

Andrew Main (Zefram) <zefram@fysh.org>

COPYRIGHT

Copyright (C) 2006, 2007, 2009, 2010, 2012 Andrew Main (Zefram) <zefram@fysh.org>

LICENSE

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.