Graph::Data(3) User Contributed Perl Documentation Graph::Data(3)NAMEGD::Graph::Data - Data set encapsulation for GD::Graph
SYNOPSIS
use GD::Graph::Data;
DESCRIPTION
This module encapsulates the data structure that is needed for
GD::Graph and friends. An object of this class contains a list of X
values, and a number of lists of corresponding Y values. This only
really makes sense if the Y values are numerical, but you can basically
store anything. Undefined values have a special meaning to GD::Graph,
so they are treated with care when stored.
Many of the methods of this module are intended for internal use by
GD::Graph and the module itself, and will most likely not be useful to
you. Many won't even seem useful to you...
EXAMPLES
use GD::Graph::Data;
use GD::Graph::bars;
my $data = GD::Graph::Data->new();
$data->read(file => '/data/sales.dat', delimiter => ',');
$data = $data->copy(wanted => [2, 4, 5]);
# Add the newer figures from the database
use DBI;
# do DBI things, like connecting to the database, statement
# preparation and execution
while (@row = $sth->fetchrow_array)
{
$data->add_point(@row);
}
my $chart = GD::Graph::bars->new();
my $gd = $chart->plot($data);
or for quick changes to legacy code
# Legacy code builds array like this
@data = ( [qw(Jan Feb Mar)], [1, 2, 3], [5, 4, 3], [6, 3, 7] );
# And we quickly need to do some manipulations on that
my $data = GD::Graph::Data->new();
$data->copy_from(\@data);
# And now do all the new stuff that's wanted.
while (@foo = bar_baz())
{
$data->add_point(@foo);
}
METHODS
$data = GD::Graph::Data->new()
Create a new GD::Graph::Data object.
$data->set_x($np, $value);
Set the X value of point $np to $value. Points are numbered starting
with 0. You probably will never need this. Returns undef on failure.
$data->get_x($np)
Get the X value of point $np. See "set_x".
$data->set_y($nd, $np, $value);
Set the Y value of point $np in data set $nd to $value. Points are
numbered starting with 0, data sets are numbered starting with 1. You
probably will never need this. Returns undef on failure.
$data->get_y($nd, $np)
Get the Y value of point $np in data set $nd. See "set_y". This will
return undef on an error, but the fact that it returns undef does not
mean there was an error (since undefined values can be stored, and
therefore returned).
$data->get_y_cumulative($nd, $np)
Get the cumulative value of point $np in data set<$nd>. The cumulative
value is obtained by adding all the values of the points $np in the
data sets 1 to $nd.
$data->get_min_max_x
Returns a list of the minimum and maximum x value or the empty list on
failure.
$data->get_min_max_y($nd)
Returns a list of the minimum and maximum y value in data set $nd or
the empty list on failure.
$data->get_min_max_y_all()
Returns a list of the minimum and maximum y value in all data sets or
the empty list on failure.
$data->add_point($X, $Y1, $Y2 ...)
Adds a point to the data set. The base for the addition is the current
number of X values. This means that if you have a data set with the
contents
(X1, X2)
(Y11, Y12)
(Y21)
(Y31, Y32, Y33, Y34)
a $data->add_point(Xx, Y1x, Y2x, Y3x, Y4x) will result in
(X1, X2, Xx )
(Y11, Y12, Y1x)
(Y21, undef, Y2x)
(Y31, Y32, Y3x, Y34)
(undef, undef, Y4x)
In other words: beware how you use this. As long as you make sure that
all data sets are of equal length, this method is safe to use.
$data->num_sets()
Returns the number of data sets.
$data->num_points()
In list context, returns a list with its first element the number of X
values, and the subsequent elements the number of respective Y values
for each data set. In scalar context returns the number of points that
have an X value set, i.e. the number of data sets that would result
from a call to "make_strict".
$data->x_values()
Return a list of all the X values.
$data->y_values($nd)
Return a list of the Y values for data set $nd. Data sets are numbered
from 1. Returns the empty list if $nd is out of range, or if the data
set at $nd is empty.
$data->reset() OR GD::Graph::Data->reset()
As an object method: Reset the data container, get rid of all data and
error messages. As a class method: get rid of accumulated error
messages and possible other crud.
$data->make_strict()
Make all data set lists the same length as the X list by truncating
data sets that are too long, and filling data sets that are too short
with undef values. always returns a true value.
$data->cumulate(preserve_undef => boolean)
The cumulate parameter will summarise the Y value sets as follows: the
first Y value list will be unchanged, the second will contain a sum of
the first and second, the third will contain the sum of first, second
and third, and so on. Returns undef on failure.
if the argument preserve_undef is set to a true value, then the sum of
exclusively undefined values will be preserved as an undefined value.
If it is not present or a false value, undef will be treated as zero.
Note that this still will leave undefined values in the first data set
alone.
Note: Any non-numerical defined Y values will be treated as 0, but you
really shouldn't be using this to store that sort of Y data.
$data->wanted(indexes)
Removes all data sets except the ones in the argument list. It will
also reorder the data sets in the order given. Returns undef on
failure.
To remove all data sets except the first, sixth and second, in that
order:
$data->wanted(1, 6, 2) or die $data->error;
$data->reverse
Reverse the order of the data sets.
$data->copy_from($data_ref)
Copy an 'old' style GD::Graph data structure or another GD::Graph::Data
object into this object. This will remove the current data. Returns
undef on failure.
$data->copy()
Returns a copy of the object, or undef on failure.
$data->read(arguments)
Read a data set from a file. This will remove the current data. returns
undef on failure. This method uses the standard module Text::ParseWords
to parse lines. If you don't have this for some odd reason, don't use
this method, or your program will die.
Data file format: The default data file format is tab separated data
(which can be changed with the delimiter argument). Comment lines are
any lines that start with a #. In the following example I have replaced
literal tabs with <tab> for clarity
# This is a comment, and will be ignored
Jan<tab>12<tab>24
Feb<tab>13<tab>37
# March is missing
Mar<tab><tab>
Apr<tab>9<tab>18
Valid arguments are:
file, mandatory. The file name of the file to read from, or a reference
to a file handle or glob.
$data->read(file => '/data/foo.dat') or die $data->error;
$data->read(file => \*DATA) or die $data->error;
$data->read(file => $file_handle) or die $data->error;
no_comment, optional. Give this a true value if you don't want lines
with an initial # to be skipped.
$data->read(file => '/data/foo.dat', no_comment => 1);
delimiter, optional. A regular expression that will become the
delimiter instead of a single tab.
$data->read(file => '/data/foo.dat', delimiter => '\s+');
$data->read(file => '/data/foo.dat', delimiter => qr/\s+/);
$data->error() OR GD::Graph::Data->error()
Returns a list of all the errors that the current object has
accumulated. In scalar context, returns the last error. If called as a
class method it works at a class level.
This method is inherited, see GD::Graph::Error for more information.
$data->has_error() OR GD::Graph::Data->has_error()
Returns true if the object (or class) has errors pending, false if not.
In some cases (see "copy") this is the best way to check for errors.
This method is inherited, see GD::Graph::Error for more information.
NOTES
As with all Modules for Perl: Please stick to using the interface. If
you try to fiddle too much with knowledge of the internals of this
module, you could get burned. I may change them at any time.
Specifically, I probably won't always keep this implemented as an array
reference.
AUTHOR
Martien Verbruggen <mgjv@tradingpost.com.au>
Copyright
(c) Martien Verbruggen.
All rights reserved. This package is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.
SEE ALSO
GD::Graph, GD::Graph::Error
perl v5.18.1 2007-04-26 Graph::Data(3)
