GD::Graph - Graph Plotting Module for Perl 5
use GD::Graph::moduleName;
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
GD::Graph::bars and GD::Graph::hbars
GD::Graph::points
GD::Graph::linespoints
GD::Graph::area
GD::Graph::mixed
Additional types:
GD::Graph::pie
See the samples directory in the distribution, and read the Makefile there.
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.
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.
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.
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.
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.
shadowclr and bar_spacing options.
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".
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) ]
undef means the border will not be drawn.
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.
options for bars, lines, points, linespoints, mixed and area charts.
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.
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.
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.
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.
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.
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].
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.
This space will be left open between text elements and the graph (text elements are title and axis labels.
Default: 8.
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.
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.
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.
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.
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.
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:
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 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
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.
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)
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
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]
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
The type of graph to draw for data sets that either have no type set, or that have an unknown type set.
Default: lines
At the moment legend support is minimal.
Methods
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.
Options
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.
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.
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).
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.
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.
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.
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:
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.
Martien Verbruggen <mgjv@tradingpost.com.au>
Current maintenance (including this release) by Benjamin Warfield <bwarfield@cpan.org>
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.
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.
GD::Graph::FAQ, GD::Graph::Data, GD::Graph::Error, GD::Graph::colour