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 can
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 ,
SEE ALSO
GD::Graph
COPYRIGHT
Copyright 2002 - 2006 Adam Kennedy.
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.