NAME
    Chart::Math::Axis - Implements an algorithm to find good values for
    chart axis

SYNOPSIS
      # Create a new Axis
      my $Axis = Chart::Math::Axis->new();

      # Provide is some data to calculate on
      $Axis->add_data( @dataset );

      # Get the values for the axis
      print "Top of axis: " . $Axis->top . "\n";
      print "Bottom of axis: " . $Axis->bottom . "\n";
      print "Tick interval: " . $Axis->interval_size . "\n";
      print "Number of ticks: " . $Axis->ticks . "\n";

      # Apply the axis directly to a GD::Graph.
      $Axis->apply_to( $Graph );

DESCRIPTION
    Chart::Math::Axis implements in a generic way an algorithm for finding a
    set of ideal values for an axis. That is, for any given set of data,
    what should the top and bottom of the axis scale be, and what should the
    interval between the ticks be.

    The terms "top" and "bottom" are used throughout this module, as it's
    primary use is for determining the Y axis. For calculating the X axis,
    you should think of 'top' as 'right', and 'bottom' as 'left'.

METHODS
  new( [ @dataset ] )
    The "new" method creates a new "Chart::Math::Axis" object. Any arguments
    passed to the constructor are used as dataset values. Whenever the
    object has some values on which to work, it will calculate the axis. If
    the object is created with no values, most methods will return undef.

  max()
    Returns the maximum value in the dataset.

  min()
    Returns the minimum value in the dataset.

  top()
    The "top" method returns the value that should be the top of the axis.

  bottom()
    The "bottom" method returns the value that should be the bottom of the
    axis.

  maximum_intervals()
    Although Chart::Math::Axis can work out scale and intervals, it doesn't
    know how many pixels you might need, how big labels etc are, so it's
    can't determine the tick density you are going to need. The
    "maximum_intervals" method returns the current value for the maximum
    number of ticks the object is allowed to have.

    To change this value, see the "set_maximum_intervals" method. The
    default for the maximum number of intervals is 10.

  interval_size()
    The "interval_size" method returns the interval size in dataset terms.

  ticks()
    The "ticks" method returns the number of intervals that the
    top/bottom/size values will result in.

  add_data( @dataset )
    The "add_data" method allows you to provide data that the object should
    be aware of when calculating the axis. In fact, you can add additional
    data at any time, and the axis will be updated as needed.

  set_maximum_intervals( $intervals )
    The "set_maximum_intervals" method takes an argument and uses it as the
    maximum number of ticks the axis is allowed to have.

  include_zero()
    If you have a dataset something like ( 10, 11, 12 ) the bottom of the
    axis will probably be somewhere around 9 or 8. That is, it won't show
    the zero axis. If you want to force the axis to include zero, use this
    method to do so.

  apply_to( $gd_graph_object )
    The "apply_to" method is intended to provide a series of shortcuts for
    automatically applying an axis to a graph of a know type. At the
    present, this will change only the Y axis of a GD::Graph object. This
    method is considered experimental. If in doubt, extract and set the
    graph values yourself.

SUPPORT
    Contact the author

AUTHOR
            Adam Kennedy ( maintainer )
            cpan@ali.as
            http://ali.as/

SEE ALSO
    GD::Graph

COPYRIGHT
    Copyright (c) 2002 Adam Kennedy. All rights reserved. This program is
    free software; you can redistribute it and/or modify it under the same
    terms as Perl itself.

    The full text of the license can be found in the LICENSE file included
    with this module.