Manual Reference Pages - CHART::MATH::AXIS (3)
Chart::Math::Axis - Implements an algorithm to find good values for chart axis
# 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 );
<B>Chart::Math::AxisB> 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 its
primary use is for determining the Y axis. For calculating the X axis,
you should think of top as right, and bottom as left.
my $null = Chart::Math::Axis->new;
my $full = Chart::Math::Axis->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.
Returns the maximum value in the dataset.
Returns the minimum value in the dataset.
The top method returns the value that should be the top of the axis.
The bottom method returns the value that should be the bottom of the axis.
Although Chart::Math::Axis can work out scale and intervals, it doesnt 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.
The interval_size method returns the interval size in dataset terms.
The ticks method returns the number of intervals that the top/bottom/size
values will result in.
$self->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.
$self->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.
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 wont show the zero
axis. If you want to force the axis to include zero, use this method to do so.
$self->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
Bugs should be reported via the CPAN bug tracker
For other issues, or commercial enhancement or support, contact the author.
Adam Kennedy <email@example.com>
Copyright 2002 - 2011 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.
|perl v5.20.3 ||CHART::MATH::AXIS (3) ||2011-03-24 |
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