NAME¶
GD::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