Ubuntu Manpage: GD::Graph - Graph Plotting Module for Perl 5

Provided by: libgd-graph-perl_1.44-6_all

NAME

       GD::Graph - Graph Plotting Module for Perl 5

SYNOPSIS

       use GD::Graph::moduleName;

DESCRIPTION

       GD::Graph is a perl5 module to create charts using the GD module.  The following classes for graphs with
       axes are defined:

       "GD::Graph::lines"
           Create a line chart.

       "GD::Graph::bars" and "GD::Graph::hbars"
           Create a bar chart with vertical or horizontal bars.

       "GD::Graph::points"
           Create an chart, displaying the data as points.

       "GD::Graph::linespoints"
           Combination of lines and points.

       "GD::Graph::area"
           Create a graph, representing the data as areas under a line.

       "GD::Graph::mixed"
           Create  a  mixed type graph, any combination of the above. At the moment this is fairly limited. Some
           of the options that can be used with some of the individual graph types won't  work  very  well.  Bar
           graphs drawn after lines or points graphs may obscure the earlier data, and specifying bar_width will
           not produce the results you probably expected.

       Additional types:

       "GD::Graph::pie"
           Create a pie chart.

EXAMPLES

       See the samples directory in the distribution, and read the Makefile there.

USAGE

       Fill an array of arrays with the x values and the values of the data sets.  Make sure that every array is
       the same size, otherwise GD::Graph will complain and refuse to compile the graph.

         @data = (
           ["1st","2nd","3rd","4th","5th","6th","7th", "8th", "9th"],
           [    1,    2,    5,    6,    3,  1.5,    1,     3,     4],
           [ sort { $a <=> $b } (1, 2, 5, 6, 3, 1.5, 1, 3, 4) ]
         );

       If  you  don't  have  a  value for a point in a certain dataset, you can use undef, and the point will be
       skipped.

       Create a new GD::Graph object by calling the new method on the graph type you want to  create  (chart  is
       bars, hbars, lines, points, linespoints, mixed or pie).

         my $graph = GD::Graph::chart->new(400, 300);

       Set the graph options.

         $graph->set(
             x_label           => 'X Label',
             y_label           => 'Y label',
             title             => 'Some simple graph',
             y_max_value       => 8,
             y_tick_number     => 8,
             y_label_skip      => 2
         ) or die $graph->error;

       and plot the graph.

         my $gd = $graph->plot(\@data) or die $graph->error;

       Then  do  whatever your current version of GD allows you to do to save the file. For versions of GD older
       than 1.19 (or more recent than 2.15), you'd do something like:

         open(IMG, '>file.gif') or die $!;
         binmode IMG;
         print IMG $gd->gif;
         close IMG;

       and for newer versions (1.20 and up) you'd write

         open(IMG, '>file.png') or die $!;
         binmode IMG;
         print IMG $gd->png;

       or

         open(IMG, '>file.gd2') or die $!;
         binmode IMG;
         print IMG $gd->gd2;

       Then there's also of course the possibility of using a shorter version (for each of the export  functions
       that GD supports):

         print IMG $graph->plot(\@data)->gif;
         print IMG $graph->plot(\@data)->png;
         print IMG $graph->plot(\@data)->gd;
         print IMG $graph->plot(\@data)->gd2;

       If  you  want  to write something that doesn't require your code to 'know' whether to use gif or png, you
       could do something like:

         if ($gd->can('png')) { # blabla }

       or you can use the convenience method "export_format":

         my $format = $graph->export_format;
         open(IMG, ">file.$format") or die $!;
         binmode IMG;
         print IMG $graph->plot(\@data)->$format();
         close IMG;

       or for CGI programs:

         use CGI qw(:standard);
         #...
         my $format = $graph->export_format;
         print header("image/$format");
         binmode STDOUT;
         print $graph->plot(\@data)->$format();

       (the parentheses after $format are necessary, to help the compiler decide that you  mean  a  method  name
       there)

       See under "SEE ALSO" for references to other documentation, especially the FAQ.

METHODS

   Methods for all graphs
       GD::Graph::chart->new([width,height])
           Create  a  new  object  $graph with optional width and heigth.  Default width = 400, default height =
           300. chart is either bars, lines, points, linespoints, area, mixed or pie.

       $graph->set_text_clr(colour name)
           Set the colour of the text. This will set the colour of the titles, labels, and axis labels to colour
           name. Also see the options textclr, labelclr and axislabelclr.

       $graph->set_title_font(font specification)
           Set the font that will be used for the title of the chart.  See "FONTS".

       $graph->plot(\@data)
           Plot the chart, and return the GD::Image object.

       $graph->set(attrib1 => value1, attrib2 => value2 ...)
           Set chart options. See OPTIONS section.

       $graph->get(attrib1, attrib2)
           Returns a list of the values of the attributes. In scalar context returns  the  value  of  the  first
           attribute only.

       $graph->gd()
           Get  the GD::Image object that is going to be used to draw on. You can do this either before or after
           calling the plot method, to do your own drawing.

           Note: as of the current version, this GD::Image object will always  be  palette-based,  even  if  the
           installed version of GD supports true-color images.

           Note  also  that  if  you  draw  on  the  GD::Image  object  before  calling the plot method, you are
           responsible for making sure that the background colour is correct and for setting transparency.

       $graph->export_format()
           Query the export format of the GD library in use.  In scalar context,  it  returns  'gif',  'png'  or
           undefined, which is sufficient for most people's use. In a list context, it returns a list of all the
           formats that are supported by the current version of GD. It can be called as a class or object method

       $graph->can_do_ttf()
           Returns  true  if the current GD library supports TrueType fonts, False otherwise. Can also be called
           as a class method or static method.

   Methods for Pie charts
       $graph->set_label_font(font specification)
       $graph->set_value_font(font specification)
           Set the font that will be used for the label of the pie or the values on the pie.  See "FONTS".

   Methods for charts with axes.
       $graph->set_x_label_font(font specification)
       $graph->set_y_label_font(font specification)
       $graph->set_x_axis_font(font specification)
       $graph->set_y_axis_font(font specification)
       $graph->set_values_font(font specification)
           Set the font for the x and y axis label, the x and y axis value labels, and for  the  values  printed
           above the data points.  See "FONTS".

       $graph->get_hotspot($dataset, $point)
           Experimental:  Return  a  coordinate  specification  for a point in a dataset. Returns a list. If the
           point is not specified, returns a list of array references for all points  in  the  dataset.  If  the
           dataset is also not specified, returns a list of array references for each data set.  See "HOTSPOTS".

       $graph->get_feature_coordinates($feature_name)
           Experimental:  Return  a  coordinate  specification  for  a certain feature in the chart.  Currently,
           features that are defined are axes, the coordinates  of  the  rectangle  within  the  axes;  x_label,
           y1_label  and  y2_label,  the  labels  printed  along the axes, with y_label provided as an alias for
           y1_label; and title which is the title text box.  See "HOTSPOTS".

OPTIONS

Options for all graphs
width, height
The width and height of the canvas in pixels Default: 400 x 300. NB At the moment, these are read-
only options. If you want to set the size of a graph, you will have to do that with the new method.

t_margin, b_margin, l_margin, r_margin
Top, bottom, left and right margin of the canvas. These margins will be left blank. Default: 0 for
all.

logo
Name of a logo file. Generally, this should be the same format as your version of GD exports images
in. Currently, this file may be in any format that GD can import, but please see GD if you use an
XPM file and get unexpected results.

Default: no logo.

logo_resize, logo_position
Factor to resize the logo by, and the position on the canvas of the logo. Possible values for
logo_position are 'LL', 'LR', 'UL', and 'UR'. (lower and upper left and right). Default: 'LR'.

transparent
If set to a true value, the produced image will have the background colour marked as transparent (see
also option bgclr). Default: 1.

interlaced
If set to a true value, the produced image will be interlaced. Default: 1.

Note: versions of GD higher than 2.0 (that is, since GIF support was restored after being removed
owing to patent issues) do not support interlacing of GIF images. Support for interlaced PNG and
progressive JPEG images remains available using this option.

Colours
bgclr, fgclr, boxclr, accentclr, shadowclr
Drawing colours used for the chart: background, foreground (axes and grid), axis box fill colour,
accents (bar, area and pie outlines), and shadow (currently only for bars).

All colours should have a valid value as described in "COLOURS", except boxclr, which can be
undefined, in which case the box will not be filled.

shadow_depth
Depth of a shadow, positive for right/down shadow, negative for left/up shadow, 0 for no shadow
(default). Also see the "shadowclr" and "bar_spacing" options.

labelclr, axislabelclr, legendclr, valuesclr, textclr
Text Colours used for the chart: label (labels for the axes or pie), axis label (misnomer: values
printed along the axes, or on a pie slice), legend text, shown values text, and all other text.

All colours should have a valid value as described in "COLOURS".

dclrs (short for datacolours)
This controls the colours for the bars, lines, markers, or pie slices. This should be a reference to
an array of colour names as defined in GD::Graph::colour ("perldoc GD::Graph::colour" for the names
available).

$graph->set( dclrs => [ qw(green pink blue cyan) ] );

The first (fifth, ninth) data set will be green, the next pink, etc.

A colour can be "undef", in which case the data set will not be drawn. This can be useful for
cumulative bar sets where you want certain data series (often the first one) not to show up, which
can be used to emulate error bars (see examples 1-7 and 6-3 in the distribution).

Default: [ qw(lred lgreen lblue lyellow lpurple cyan lorange) ]

borderclrs
This controls the colours of the borders of the bars data sets. Like dclrs, it is a reference to an
array of colour names as defined in GD::Graph::colour. Setting a border colour to "undef" means the
border will not be drawn.

cycle_clrs
If set to a true value, bars will not have a colour from "dclrs" per dataset, but per point. The
colour sequence will be identical for each dataset. Note that this may have a weird effect if you are
drawing more than one data set. If this is set to a value larger than 1 the border colour of the bars
will cycle through the colours in "borderclrs".

accent_treshold
Not really a colour, but it does control a visual aspect: Accents on bars are only drawn when the
width of a bar is larger than this number of pixels. Accents inside areas are only drawn when the
horizontal distance between points is larger than this number. Default 4

Options for graphs with axes.
options for bars, lines, points, linespoints, mixed and area charts.

x_label, y_label
The labels to be printed next to, or just below, the axes. Note that if you use the two_axes option
that you need to use y1_label and y2_label.

long_ticks, tick_length
If long_ticks is a true value, ticks will be drawn the same length as the axes. Otherwise ticks will
be drawn with length tick_length. if tick_length is negative, the ticks will be drawn outside the
axes. Default: long_ticks = 0, tick_length = 4.

These attributes can also be set for x and y axes separately with x_long_ticks, y_long_ticks,
x_tick_length and y_tick_length.

x_ticks
If x_ticks is a true value, ticks will be drawm for the x axis. These ticks are subject to the
values of long_ticks and tick_length. Default: 1.

y_tick_number
Number of ticks to print for the Y axis. Use this, together with y_label_skip to control the look of
ticks on the y axis. Default: 5.

y_number_format
This can be either a string, or a reference to a subroutine. If it is a string, it will be taken to
be the first argument to a sprintf, with the value as the second argument:

$label = sprintf( $s->{y_number_format}, $value );

If it is a code reference, it will be executed with the value as the argument:

$label = &{$s->{y_number_format}}($value);

This can be useful, for example, if you want to reformat your values in currency, with the - sign in
the right spot. Something like:

sub y_format
{
my $value = shift;
my $ret;

if ($value >= 0)
{
$ret = sprintf("\$%d", $value * $refit);
}
else
{
$ret = sprintf("-\$%d", abs($value) * $refit);
}

return $ret;
}

$graph->set( 'y_number_format' => \&y_format );

(Yes, I know this can be much shorter and more concise)

Default: undef.

y1_number_format, y2_number_format
As with y_number_format, these can be either a string, or a reference to a subroutine. These are used
as formats for graphs with two y-axis scales so that independent formats can be used.

For compatibility purposes, each of these will fall back on y_number_format if not specified.

Default: undef for both.

x_label_skip, y_label_skip
Print every x_label_skipth number under the tick on the x axis, and every y_label_skipth number next
to the tick on the y axis. Default: 1 for both.

x_tick_offset
When x_label_skip is used, this will skip the first x_tick_offset values in the labels before
starting to print. Let me give an example. If you have a series of X labels like

qw(Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec)

and you set x_label_skip to 3, you will see ticks on the X axis for Jan, Apr, Jul, Oct and Dec. This
is not always what is wanted. If you set x_tick_offset to 1, you get Feb, May, Aug, Nov and Dec, and
if you set it to 2, you get Mar, Jun Sep and Dec, and this last one definitely looks better. A
combination of 6 and 5 also works nice for months.

Note that the value for x_tick_offset is periodical. This means that it will have the same effect for
each nteger n in x_tick_offset + n * x_label_skip.

x_all_ticks
Force a print of all the x ticks, even if x_label_skip is set to a value Default: 0.

x_label_position
Controls the position of the X axis label (title). The value for this should be between 0 and 1,
where 0 means aligned to the left, 1 means aligned to the right, and 1/2 means centered. Default:
3/4

y_label_position
Controls the position of both Y axis labels (titles). The value for this should be between 0 and 1,
where 0 means aligned to the bottom, 1 means aligned to the top, and 1/2 means centered. Default:
1/2

x_labels_vertical
If set to a true value, the X axis labels will be printed vertically. This can be handy in case
these labels get very long. Default: 0.

x_plot_values, y_plot_values
If set to a true value, the values of the ticks on the x or y axes will be plotted next to the tick.
Also see x_label_skip, y_label_skip. Default: 1 for both.

box_axis
Draw the axes as a box, if true. Default: 1.

no_axes
Draw no axes at all. If this is set to undef, all axes are drawn. If it is set to 0, the zero axis
will be drawn, for bar charts only. If this is set to a true value, no axes will be drawns at all.
Value labels on the axes and ticks will also not be drawn, but axis lables are drawn. Default:
undef.

two_axes
Use two separate axes for the first and second data set. The first data set will be set against the
left axis, the second against the right axis. If more than two data sets are being plotted, the
use_axis option should be used to specify which data sets use which axis.

Note that if you use this option, that you need to use y1_label and y2_label, instead of just
y_label, if you want the two axes to have different labels. The same goes for some other options
starting with the letter 'y' and an underscore.

Default: 0.

use_axis
If two y-axes are in use and more than two datasets are specified, set this option to an array
reference containing a value of 1 or 2 (for the left and right scales respectively) for each dataset
being plotted. That is, to plot three datasets with the second on a different scale than the first
and third, set this to "[1,2,1]".

Default: [1,2].

zero_axis
If set to a true value, the axis for y values of 0 will always be drawn. This might be useful in case
your graph contains negative values, but you want it to be clear where the zero value is. (see also
zero_axis_only and box_axes). Default: 0.

zero_axis_only
If set to a true value, the zero axis will be drawn (see zero_axis), and no axis at the bottom of the
graph will be drawn. The labels for X values will be placed on the zero exis. Default: 0.

y_max_value, y_min_value
Maximum and minimum value displayed on the y axis. If two_axes is a true value, then y1_min_value,
y1_max_value (for the left axis), and y2_min_value, y2_max_value (for the right axis) take precedence
over these.

The range (y_min_value..y_max_value) has to include all the values of the data points, or GD::Graph
will die with a message.

For bar and area graphs, the range (y_min_value..y_max_value) has to include 0. If it doesn't, the
values will be adapted before attempting to draw the graph.

Default: Computed from data sets.

axis_space
This space will be left blank between the axes and the tick value text. Default: 4.

text_space
This space will be left open between text elements and the graph (text elements are title and axis
labels.

Default: 8.

cumulate
If this attribute is set to a true value, the data sets will be cumulated. This means that they will
be stacked on top of each other. A side effect of this is that "overwrite" will be set to a true
value.

Notes: This only works for bar and area charts at the moment.

If you have negative values in your data sets, setting this option might produce odd results. Of
course, the graph itself would be quite meaningless.

overwrite
If set to 0, bars of different data sets will be drawn next to each other. If set to 1, they will be
drawn in front of each other. Default: 0.

Note: Setting overwrite to 2 to produce cumulative sets is deprecated, and may disappear in future
versions of GD::Graph. Instead see the "cumulate" attribute.

correct_width
If this is set to a true value and "x_tick_number" is false, then the width of the graph (or the
height for rotated graphs like "GD::Graph::hbar") will be recalculated to make sure that each data
point is exactly an integer number of pixels wide. You probably never want to fiddle with this.

When this value is true, you will need to make sure that the number of data points is smaller than
the number of pixels in the plotting area of the chart. If you get errors saying that your horizontal
size if too small, you may need to manually switch this off, or consider using something else than a
bar type for your chart.

Default: 1 for bar, calculated at runtime for mixed charts, 0 for others.

Plotting data point values with the data point
Sometimes you will want to plot the value of a data point or bar above the data point for clarity.
GD::Graph allows you to control this in a generic manner, or even down to the single point.

show_values
Set this to 1 to display the value of each data point above the point or bar itself. No effort is
being made to ensure that there is enough space for the text.

Set this to a GD::Graph::Data object, or an array reference of the same shape, with the same
dimensions as your data object that you pass in to the plot method. The reason for this option is
that it allows you to make a copy of your data set, and selectively set points to "undef" to disable
plotting of them.

my $data = GD::Graph::Data->new(
[ [ 'A', 'B', 'C' ], [ 1, 2, 3 ], [ 11, 12, 13 ] ]);
my $values = $data->copy;
$values->set_y(1, 1, undef);
$values->set_y(2, 0, undef);

$graph->set(show_values => $values);
$graph->plot($data);

Default: 0.

values_vertical
If set to a true value, the values will be printed vertically, instead of horizontally. This can be
handy if the values are long numbers. Default: 0.

values_space
Space to insert between the data point and the value to print. Default: 4.

values_format
How to format the values for display. See y_number_format for more information. Default: undef.

Options for graphs with a numerical X axis
First of all: GD::Graph does not support numerical x axis the way it should. Data for X axes should be
equally spaced. That understood: There is some support to make the printing of graphs with numerical X
axis values a bit better, thanks to Scott Prahl. If the option "x_tick_number" is set to a defined value,
GD::Graph will attempt to treat the X data as numerical.

Extra options are:

x_tick_number
If set to 'auto', GD::Graph will attempt to format the X axis in a nice way, based on the actual X
values. If set to a number, that's the number of ticks you will get. If set to undef, GD::Graph will
treat X data as labels. Default: undef.

x_min_value, x_max_value
The minimum and maximum value to use for the X axis. Default: computed.

x_number_format
See y_number_format

x_label_skip
See y_label_skip

Options for graphs with bars
bar_width
The width of a bar in pixels. Also see "bar_spacing". Use "bar_width" If you want to have fixed-
width bars, no matter how wide the chart gets. Default: as wide as possible, within the constraints
of the chart size and "bar_spacing" setting.

bar_spacing
Number of pixels to leave open between bars. This works well in most cases, but on some platforms, a
value of 1 will be rounded off to 0. Use "bar_spacing" to get a fixed amount of space between bars,
with variable bar widths, depending on the width of the chart. Note that if "bar_width" is also set,
this setting will be ignored, and automatically calculated. Default: 0

bargroup_spacing
Number of pixels (in addition to whatever is specified in "bar_spacing") to leave between groups of
bars when multiple datasets are being displayed. Unlike "bar_spacing", however, this parameter will
hold its value if "bar_width" is set.

Options for graphs with lines
line_types
Which line types to use for lines and linespoints graphs. This should be a reference to an array of
numbers:

$graph->set( line_types => [3, 2, 4] );

Available line types are 1: solid, 2: dashed, 3: dotted, 4: dot-dashed.

Default: [1] (always use solid)

line_type_scale
Controls the length of the dashes in the line types. default: 6.

line_width
The width of the line used in lines and linespoints graphs, in pixels. Default: 1.

skip_undef
For all other axes graph types, the default behaviour is (by their nature) to not draw a point when
the Y value is "undef". For line charts the point gets skipped as well, but the line is drawn between
the points n-1 to n+1 directly. If "skip_undef" has a true value, there will be a gap in the chart
where a Y value is undefined.

Note that a line will not be drawn unless there are at least two consecutive data points exist that
have a defined value. The following data set will only plot a very short line towards the end if
"skip_undef" is set:

@data = (
[ qw( Jan Feb Mar Apr May Jun Jul Aug Sep Oct ) ],
[ 1, undef, 2, undef, 3, undef, 4, undef, 5, 6 ]
);

This option is useful when you have a consecutive gap in your data, or with linespoints charts. If
you have data where you have intermittent gaps, be careful when you use this. Default value: 0

Options for graphs with points
markers
This controls the order of markers in points and linespoints graphs. This should be a reference to
an array of numbers:

$graph->set( markers => [3, 5, 6] );

Available markers are: 1: filled square, 2: open square, 3: horizontal cross, 4: diagonal cross, 5:
filled diamond, 6: open diamond, 7: filled circle, 8: open circle, 9: horizontal line, 10: vertical
line. Note that the last two are not part of the default list.

Default: [1,2,3,4,5,6,7,8]

marker_size
The size of the markers used in points and linespoints graphs, in pixels. Default: 4.

Options for mixed graphs
types
A reference to an array with graph types, in the same order as the data sets. Possible values are:

$graph->set( types => [qw(lines bars points area linespoints)] );
$graph->set( types => ['lines', undef, undef, 'bars'] );

values that are undefined or unknown will be set to "default_type".

Default: all set to "default_type"

default_type
The type of graph to draw for data sets that either have no type set, or that have an unknown type
set.

Default: lines

Graph legends (axestype graphs only)
At the moment legend support is minimal.

Methods

$graph->set_legend(@legend_keys);
Sets the keys for the legend. The elements of @legend_keys correspond to the data sets as provided to
plot().

If a key is undef or an empty string, the legend entry will be skipped.

$graph->set_legend_font(font name);
Sets the font for the legend text (see "FONTS"). Default: GD::gdTinyFont.

Options

legend_placement
Where to put the legend. This should be a two letter key of the form: 'B[LCR]|R[TCB]'. The first
letter indicates the placement (Bottom or Right), and the second letter the alignment (Left, Right,
Center, Top, or Bottom). Default: 'BC'

If the legend is placed at the bottom, some calculations will be made to ensure that there is some
'intelligent' wrapping going on. if the legend is placed at the right, all entries will be placed
below each other.

legend_spacing
The number of pixels to place around a legend item, and between a legend 'marker' and the text.
Default: 4

legend_marker_width, legend_marker_height
The width and height of a legend 'marker' in pixels. Defaults: 12, 8

lg_cols
If you, for some reason, need to force the legend at the bottom to have a specific number of columns,
you can use this. Default: computed

Options for pie graphs
3d If set to a true value, the pie chart will be drawn with a 3d look. Default: 1.

pie_height
The thickness of the pie when 3d is true. Default: 0.1 x height.

start_angle
The angle at which the first data slice will be displayed, with 0 degrees being "6 o'clock".
Default: 0.

suppress_angle
If a pie slice is smaller than this angle (in degrees), a label will not be drawn on it. Default: 0.

label
Print this label below the pie. Default: undef.

COLOURS

       All  references to colours in the options for this module have been shortened to clr. The main reason for
       this was that I didn't want to support two spellings for the same word ('colour' and 'color')

       Wherever a colour is required,  a  colour  name  should  be  used  from  the  package  GD::Graph::colour.
       "perldoc GD::Graph::colour"  should  give  you  the  documentation  for that module, containing all valid
       colour names. I will probably change this to read the systems rgb.txt file if it is available.

FONTS

       Depending on your version of GD, this accepts both GD builtin fonts or the name of a TrueType font  file.
       In  the  case of a TrueType font, you must specify the font size. See GD::Text for more details and other
       things, since all font handling in GD::Graph is delegated to there.

       Examples:

           $graph->set_title_font('/fonts/arial.ttf', 18);
           $graph->set_legend_font(gdTinyFont);
           $graph->set_legend_font(
               ['verdana', 'arial', gdMediumBoldFont], 12)

       (The above discussion is based on GD::Text 0.65. Older versions have more restrictive behaviour).

HOTSPOTS

Note that this is an experimental feature, and its interface may, and likely will, change in the future.
It currently does not work for area charts or pie charts.

GD::Graph keeps an internal set of coordinates for each data point and for certain features of a chart,
like the title and axis labels. This specification is very similar to the HTML image map specification,
and in fact exists mainly for that purpose. You can get at these hotspots with the "get_hotspot" method
for data point, and "get_feature_coordinates" for the chart features.

The <get_hotspot> method accepts two optional arguments, the number of the dataset you're interested in,
and the number of the point in that dataset you're interested in. When called with two arguments, the
method returns a list of one of the following forms:

'rect', x1, y1, x2, y2
'poly', x1, y1, x2, y2, x3, y3, ....
'line', xs, ys, xe, ye, width

The parameters for "rect" are the coordinates of the corners of the rectangle, the parameters for "poly"
are the coordinates of the vertices of the polygon, and the parameters for the "line" are the coordinates
for the start and end point, and the line width. It should be possible to almost directly translate
these lists into HTML image map specifications.

If the second argument to "get_hotspot" is omitted, a list of references to arrays will be returned. This
list represents all the points in the dataset specified, and each array referred to is of the form
outlined above.

['rect', x1, y1, x2, y2 ], ['rect', x1, y1, x2, y2], ...

if both arguments to "get_hotspot" are omitted, the list that comes back will contain references to
arrays for each data set, which in turn contain references to arrays for each point.

[
['rect', x1, y1, x2, y2 ], ['rect', x1, y1, x2, y2], ...
],
[
['line', xs, ys, xe, ye, w], ['line', xs, ys, xe, ye, w], ...
],...

The "get_feature" method, when called with the name of a feature, returns a single array reference with a
type and coordinates as described above. When called with no arguments, a hash reference is returned with
the keys being all the currently defined and set features, and the values array references with the type
and coordinates for each of those features.

ERROR HANDLING

       GD::Graph  objects  inherit from the GD::Graph::Error class (not the other way around), so they behave in
       the same manner. The main feature of that behaviour is that you have the error() method available to  get
       some  information  about what went wrong. The GD::Graph methods all return undef if something went wrong,
       so you should be able to write safe programs like this:

         my $graph = GD::Graph->new()    or die GD::Graph->error;
         $graph->set( %attributes )      or die $graph->error;
         $graph->plot($gdg_data)         or die $graph->error;

       More advanced usage is possible, and there are some caveats with  this  error  handling,  which  are  all
       explained in GD::Graph::Error.

       Unfortunately,  it  is  almost impossible to gracefully recover from an error in GD::Graph, so you really
       should get rid of the object, and recreate it from scratch if you want to recover. For example, to adjust
       the correct_width attribute if you get the error "Horizontal size too small" or "Vertical size too small"
       (in the case of hbar), you could do something like:

         sub plot_graph
         {
             my $data    = shift;
             my %attribs = @_;
             my $graph   = GD::Graph::bars->new()
                or die GD::Graph->error;
             $graph->set(%attribs)     or die $graph->error;
             $graph->plot($data)       or die $graph->error;
         }

         my $gd;
         eval { $gd = plot_graph(\@data, %attribs) };
         if ($@)
         {
             die $@ unless $@ =~ /size too small/;
             $gd = plot_graph(\@data, %attribs, correct_width => 0);
         }

       Of course, you could also adjust the width this way, and you can check for other errors.

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.

BUGS

GD::Graph objects cannot be reused. To create a new plot, you have to create a new GD::Graph object.

Rotated charts (ones with the X axis on the left) can currently only be created for bars. With a little
work, this will work for all others as well. Please, be patient :)

Other outstanding bugs can (alas) probably be found in the RT queue for this distribution, at
http://rt.cpan.org/Public/Dist/Display.html?Name=GDGraph

If you think you have found a bug, please check first to see if it has already been reported. If it has
not, please do (you can use the web interface above or send e-mail to <bug-GDGraph@rt.cpan.org>). Bug
reports should contain as many as possible of the following:

• a concise description of the buggy behavior and how it differs from what you expected,

• the versions of Perl, GD::Graph and GD that you are using,

• a short demonstration script that shows the bug in action,

• a patch that fixes it. :-)

Of all of these, the third is probably the single most important, since producing a test case generally
makes the explanation much more concise and understandable, as well as making it much simpler to show
that the bug has been fixed. As an incidental benefit, if the bug is in fact caused by some code outside
of GD::Graph, it will become apparent while you are writing the test case, thereby saving time and
confusion for all concerned.

AUTHOR

       Martien Verbruggen <mgjv@tradingpost.com.au>

       Current maintenance (including this release) by Benjamin Warfield <bwarfield@cpan.org>

   Copyright
        GIFgraph: Copyright (c) 1995-1999 Martien Verbruggen.
        Chart::PNGgraph: Copyright (c) 1999 Steve Bonds.
        GD::Graph: Copyright (c) 1999 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.

   Acknowledgements
       Thanks  to  Steve Bonds for releasing Chart::PNGgraph, and keeping the code alive when GD reached version
       1.20, and I didn't have time to do something about it.

       Thanks to the following people for contributing code, or sending me fixes:  Dave  Belcher,  Steve  Bonds,
       Mike  Bremford, Damon Brodie, Gary Deschaines, brian d foy, Edwin Hildebrand, Ari Jolma, Tim Meadowcroft,
       Honza Pazdziora, Scott Prahl, Ben Tilly, Vegard Vesterheim, Jeremy Wadsack.

       And some people whose real name I don't know, and whose email address I'd rather  not  publicise  without
       their consent.