Chart(3) User Contributed Perl Documentation Chart(3)NAMEChart - a series of charting modules
SYNOPSIS
use Chart::type; (type is one of: Points, Lines, Bars, LinesPoints, Composite,
StackedBars, Mountain, Pie, HorizontalBars, Split, ErrorBars, Pareto, Direction)
$obj = Chart::type->new;
$obj = Chart::type->new ( $png_width, $png_height );
$obj->set ( $key_1, $val_1, ... ,$key_n, $val_n );
$obj->set ( $key_1 => $val_1,
...
$key_n => $val_n );
$obj->set ( %hash );
# GIFgraph.pm-style API to produce png formatted charts
@data = ( \@x_tick_labels, \@dataset1, ... , \@dataset_n );
$obj->png ( "filename", \@data );
$obj->png ( $filehandle, \@data );
$obj->png ( FILEHANDLE, \@data );
$obj->cgi_png ( \@data );
# Graph.pm-style API
$obj->add_pt ($label, $val_1, ... , $val_n);
$obj->add_dataset ($val_1, ... , $val_n);
$obj->png ( "filename" );
$obj->png ( $filehandle );
$obj->png ( FILEHANDLE );
$obj->cgi_png ();
The similar functions are available for j-peg
# Retrieve image map information
$obj->set ( 'imagemap' => 'true' );
$imagemap_ref = $obj->imagemap_dump ();
DESCRIPTION
These man-pages give you the most important information about Chart.
There is also a complete documentation (Documentation.pdf) within the
Chart package. Look at it to get more information. This module is an
attempt to build a general purpose graphing module that is easily
modified and expanded. I borrowed most of the API from Martien
Verbruggen's GIFgraph module. I liked most of GIFgraph, but I thought
it was to difficult to modify, and it was missing a few things that I
needed, most notably legends. So I decided to write a new module from
scratch, and I've designed it from the bottom up to be easy to modify.
Like GIFgraph, Chart uses Lincoln Stein's GD module for all of its
graphics primitives calls.
use-ing Chart
Okay, so you caught me. There's really no Chart::type module. All of
the different chart types (Points, Lines, Bars, LinesPoints, Composite,
StackedBars, Pie, Pareto, HorizontalBars, Split, ErrorBars, Direction
and Mountain so far) are classes by themselves, each inheriting a bunch
of methods from the Chart::Base class. Simply replace the word type
with the type of chart you want and you're on your way. For example,
use Chart::Lines;
would invoke the lines module.
Getting an object
The new method can either be called without arguments, in which case it
returns an object with the default image size (400x300 pixels), or you
can specify the width and height of the image. Just remember to
replace type with the type of graph you want. For example,
$obj = Chart::Bars->new (600,400);
would return a Chart::Bars object containing a 600x400 pixel image.
New also initializes most of the default variables, which you can
subsequently change with the set method.
Setting different options
This is where the fun begins. Set looks for a hash of keys and values.
You can pass it a hash that you've already constructed, like
%hash = ('title' => 'Foo Bar');
$obj->set (%hash);
or you can try just constructing the hash inside the set call, like
$obj->set ('title' => 'Foo Bar');
The following are all of the currently supported options:
'transparent'
Makes the background of the image transparent if set to 'true'.
Useful for making web page images. Default is 'false'.
'png_border'
Sets the number of pixels used as a border between the graph and
the edges of the png/j-peg. Defaults to 10.
'graph_border'
Sets the number of pixels used as a border between the title/labels
and the actual graph within the png. Defaults to 10.
'text_space'
Sets the amount of space left on the sides of text, to make it more
readable. Defaults to 2.
'title'
Tells GD graph what to use for the title of the graph. If empty,
no title is drawn. It recognizes '\n' as a newline, and acts
accordingly. Remember, if you want to use normal quotation marks
instead of single quotation marks then you have to quote "\\n".
Default is empty.
'sub_title'
Write a sub-title under the title in smaller letters.
'x_label'
Tells Chart what to use for the x-axis label. If empty, no label
is drawn. Default is empty.
'y_label', 'y_label2'
Tells Chart what to use for the y-axis labels. If empty, no label
is drawn. Default is empty.
'legend'
Specifies the placement of the legend. Valid values are 'left',
'right', 'top', 'bottom'. Setting this to 'none' tells chart not
to draw a legend. Default is 'right'.
'legend_labels'
Sets the values for the labels for the different data sets. Should
be assigned a reference to an array of labels. For example,
@labels = ('foo', 'bar');
$obj->set ('legend_labels' => \@labels);
Default is empty, in which case 'Dataset 1', 'Dataset 2', etc. are
used as the labels.
'tick_len'
Sets the length of the x- and y-ticks in pixels. Default is 4.
'x_ticks'
Specifies how to draw the x-tick labels. Valid values are
'normal', 'staggered' (staggers the labels vertically), and
'vertical' (the labels are draw upwards). Default is 'normal'.
'xy_plot'
Forces Chart to plot a x-y-graph, which means, that the x-axis is
also numeric if set to 'true'. Very useful for mathematical graphs.
Works for Lines, Points, LinesPoints and ErrorBars. Split makes
always a xy_plot. Defaults to 'false'.
'min_y_ticks'
Sets the minimum number of y_ticks to draw when generating a scale.
Default is 6, The minimum is 2.
'max_y_ticks'
Sets the maximum number of y_ticks to draw when generating a scale.
Default is 100. This limit is used to avoid plotting an
unreasonable large number of ticks if non-round values are used for
the min_val and max_val.
The value for 'max_y_ticks' should be at least 5 times larger than
'min_y_ticks'.
'max_x_ticks', 'min_x_ticks'
Work similar as 'max_y_ticks' and 'min_y_ticks'. Of course, only
for a xy_plot.
'integer_ticks_only'
Specifies how to draw the x- and y-ticks: as floating point
('false', '0') or as integer numbers ('true', 1). Default: 'false'
'skip_int_ticks'
If 'integer_ticks_only' was set to 'true' the labels and ticks will
be drawn every nth tick. Of course in horizontalBars it affects the
x-axis. Default to 1, no skipping.
'precision'
Sets the number of numerals after the decimal point. Affects in
most cases the y-axis. But also the x-axis if 'xy_plot' was set and
also the labels in a pie chart. Defaults to 3.
'max_val'
Sets the maximum y-value on the graph, overriding the normal auto-
scaling. Default is undef.
'min_val'
Sets the minimum y-value on the graph, overriding the normal auto-
scaling. Default is undef.
Caution should be used when setting 'max_val' and 'min_val' to
floating point or non-round numbers. This is because the scale must
start & end on a tick, ticks must have round-number intervals, and
include round numbers.
Example: Suppose your data set has a range of 35-114 units. If you
specify them as the 'min_val' & 'max_val', the y_axis will be
plotted with 80 ticks every 1 unit.. If no 'min_val' & 'max_val',
the system will auto scale the range to 30-120 with 10 ticks every
10 units.
If the 'min_val' & 'max_val' are specified to excessive precision,
they may be overridden by the system, plotting a maximum
'max_y_ticks' ticks.
'include_zero'
If 'true', forces the y-axis to include zero if it is not in the
dataset range. Default is 'false'.
In general, it is better to use this, than to set the 'min_val' if
that is all you want to achieve.
'pt_size'
Sets the radius of the points (for Chart::Points, etc.) in pixels.
Default is 18.
'brush_size'
Sets the width of the lines (for Chart::Lines, etc.) in pixels.
Default is 6.
'brushStyle'
Sets the shape of points for Chart::Points, Chart::LinesPoints.
The possibilities are 'FilledCircle', 'circle', 'donut',
'OpenCircle', 'fatPlus', 'triangle', 'upsidedownTriangle',
'square', 'hollowSquare', 'OpenRectangle', 'FilledDiamond',
'OpenDiamond', 'Star', 'OpenStar'. Default: 'FilledCircle
'skip_x_ticks'
Sets the number of x-ticks and x-tick labels to skip. (ie. if
'skip_x_ticks' was set to 4, Chart would draw every 4th x-tick and
x-tick label). Default is undef.
'custom_x_ticks'
Used in points, lines, linespoints, errorbars and bars charts, this
option allows you to you to specify exactly which x-ticks and
x-tick labels should be drawn. It should be assigned a reference
to an array of desired ticks. Just remember that I'm counting from
the 0th element of the array. (ie., if 'custom_x_ticks' is
assigned [0,3,4], then the 0th, 3rd, and 4th x-ticks will be
displayed)
'f_x_tick'
Needs a reference to a function which uses the x-tick labels
generated by the '@data->[0]' as the argument. The result of this
function can reformat the labels. For instance
$obj -> set ('f_x_tick' => \&formatter );
An example for the function formatter: x labels are seconds since
an event. The referenced function can transform this seconds to
hour, minutes and seconds.
'f_y_tick'
The same situation as for 'f_x_tick' but now used for y labels.
'colors'
This option lets you control the colors the chart will use. It
takes a reference to a hash. The hash should contain keys mapped
to references to arrays of rgb values. For instance,
$obj->set('colors' => {'background' => [255,255,255]});
sets the background color to white (which is the default). Valid
keys for this hash are
'background' (background color for the png)
'title' (color of the title)
'text' (all the text in the chart)
'x_label' (color of the x-axis label)
'y_label' (color of the first y axis label)
'y_label2' (color of the second y axis label)
'grid_lines' (color of the grid lines)
'x_grid_lines' (color of the x grid lines - for x axis ticks)
'y_grid_lines' (color of the y grid lines - for to left y axis ticks)
'y2_grid_lines' (color of the y2 grid lines - for right y axis ticks)
'dataset0'..'dataset63' (the different datasets)
'misc' (everything else, ie. ticks, box around the legend)
NB. For composite charts, there is a limit of 8 datasets per
component. The colors for 'dataset8' through 'dataset15' become
the colors for 'dataset0' through 'dataset7' for the second
component chart.
'title_font'
This option changes the font of the title. The key has to be a GD
font. eg. GD::Font->Large
'label_font'
This option changes the font of the labels. The key has to be a GD
font.
'legend_font'
This option changes the font of the text in the legend. The key
has to be a GD font.
'tick_label_font'
This is the font for the tick labels. It also needs a GD font
object as an argument.
'grey_background'
Puts a nice soft grey background on the actual data plot when set
to 'true'. Default is 'true'.
'y_axes'
Tells Chart where to place the y-axis. Has no effect on Composite
and Pie. Valid values are 'left', 'right' and 'both'. Defaults to
'left'.
'x_grid_lines'
Draws grid lines matching up to x ticks if set to 'true'. Default
is false.
'y_grid_lines'
Draws grid lines matching up to y ticks if set to 'true'. Default
is false.
'grid_lines'
Draws grid lines matching up to x and y ticks.
'spaced_bars'
Leaves space between the groups of bars at each data point when set
to 'true'. This just makes it easier to read a bar chart. Default
is 'true'.
'imagemap'
Lets Chart know you're going to ask for information about the
placement of the data for use in creating an image map from the
png. This information can be retrieved using the imagemap_dump()
method. NB. that the imagemap_dump() method cannot be called until
after the Chart has been generated (ie. using the png() or
cgi_png() methods).
'sort'
In a xy-plot, the data will be sorted ascending if set to 'true'.
(Should be set if the data isn't sorted, especially in Lines, Split
and LinesPoints) In a Pareto Chart the data will be sorted
descending. Defaults to 'false'.
'composite_info'
This option is only used for composite charts. It contains the
information about which types to use for the two component charts,
and which datasets belong to which component chart. It should be a
reference to an array of array references, containing information
like the following
$obj->set ('composite_info' => [ ['Bars', [1,2]],
['Lines', [3,4] ] ]);
This example would set the two component charts to be a bar chart
and a line chart. It would use the first two data sets for the bar
chart (note that the numbering starts at 1, not zero like most of
the other numbered things in Chart), and the second two data sets
for the line chart. The default is undef.
NB. Chart::Composite can only do two component charts.
'min_val1', 'min_val2'
Only for composite charts, these options specify the minimum
y-value for the first and second components respectively. Both
default to undef.
'max_val1', 'max_val2'
Only for composite charts, these options specify the maximum
y-value for the first and second components respectively. Both
default to undef.
'ylabel2'
The label for the right y-axis (the second component chart) on a
composite chart. Default is undef.
'y_ticks1', 'y_ticks2'
The number of y ticks to use on the first and second y-axis on a
composite chart. Please note that if you just set the 'y_ticks'
option, both axes will use that number of y ticks. Both default to
undef.
'f_y_ticks1', 'f_y_ticks2'
Only for composite charts, needs a reference to a function which
has one argument and has to return a string which labels the first
resp. second y axis. Both default to undef.
'same_y_axes'
Forces both component charts in a composite chart to use the same
maximum and minimum y-values if set to 'true'. This helps to keep
the composite charts from being too confusing. Default is undef.
'no_cache'
Adds Pragma: no-cache to the http header. Be careful with this
one, as Netscape 4.5 is unfriendly with POST using this method.
'legend_example_size'
Sets the length of the example line in the legend in pixels.
Defaults to 20.
'same_error'
This is a option only for ErrorBars. It tells chart that you want
use the same error value of a data point if set to 'true'. Look at
the documentation to see how the module ErrorBars works. Default:
'false'.
'skip_y_ticks'
Does the same for the y-axis at a HorizontalBars chart as
'skip_x_ticks' does for other charts. Defaults to 1.
'label_values'
Tells a pie chart what labels to draw beside the pie. Valid values
are 'percent', 'value', 'both' and 'none'. Defaults to 'percent'.
'legend_label_values'
Tells a pie chart what labels to draw in the legend. Valid values
are 'percent', 'value', 'both' and 'none'. Defaults to 'value'.
'start'
Required value for a split chart. Sets the start value of the first
interval. If the x coordinate of the first data point is zero, you
should 'set' to zero. Default is 'undef'.
'interval'
Also a required value for a split chart. It sets the interval of
one line to plot. Defaults 'undef'.
'interval_ticks'
Sets the number of ticks for the x-axis of a Split chart. Defaults
to 5.
'scale'
Every y-value of a split chart will be multiplied with that value,
but the scale won't change. Which means that split allows one to
overdraw certain rows! Only useful if you want to give prominence
to the maximal amplitudes of the data. Defaults to 1.
'point'
Indicates to draw points in a direction chart. 'true' or 'false'
possible. Defaults to 'true'.
'line'
If you turn this option to 'true', then direction will connect the
points with lines. Defaults to 'false'.
'arrow'
This is also an option for the direction module. If set to 'true',
chart will draw a arrow from the center to the point. Defaults to
'false'.
'angle_interval'
This option tells direction, how many angle lines should be drawn.
The default value is 30, which means that a line will be drawn
every 30 degrees. Valid Values are: 0, 5, 10, 15, 20, 30, 45 and
60. If you choose 0, direction will draw no line.
'min_circles'
Sets the minimum number of circles when generating a scale for
direction. Default is 4, minimum is 2.
'max_circles'
Sets the maximum number of circles when generating a scale for
direction. Default is 100. This limit is used to avoid plotting
an unreasonable large number of ticks if non-round values are used
for the min_val and max_val.
'pairs'
Only used for direction how to handle more datasets.
If 'pairs' is set to 'true',
Chart uses the first dataset as a set of degrees and
the second dataset as a set of values.
Then, the third set is a set of degrees and the
fourth a set of values \dots. \\
If 'pairs' is set to 'false',
Chart uses the first dataset as a set of angels
and all following datasets as sets of values.
Defaults to 'false'.
Sets the maximum number of circles when generating a scale for
direction. Default is 100. This limit is used to avoid plotting
an unreasonable large number of ticks if non-round values are used
for the min_val and max_val.
GIFgraph.pm-style API
Sending the image to a file
Invoking the png method causes the graph to be plotted and saved to
a file. It takes the name of the output file and a reference to
the data as arguments. For example,
$obj->png ("foo.png", \@data);
would plot the data in @data, and the save the image to foo.png.
Of course, this then beggars the question "What should @data look
like?". Well, just like GIFgraph, @data should contain references
to arrays of data, with the first array reference pointing to an
array of x-tick labels. For example,
@data = ( [ 'foo', 'bar', 'junk' ],
[ 30.2, 23.5, 92.1 ] );
would set up a graph with one dataset, and three data points in
that set. In general, the @data array should look something like
@data = ( \@x_tick_labels, \@dataset1, ... , \@dataset_n );
And no worries, I make my own internal copy of the data, so that it
doesn't mess with yours.
CGI and Chart
Okay, so you're probably thinking, "Do I always have to save these
images to disk? What if I want to use Chart to create dynamic
images for my web site?" Well, here's the answer to that.
$obj->cgi_png ( \@data );
The cgi_png method will print the chart, along with the appropriate
http header, to stdout, allowing you to call chart-generating
scripts directly from your html pages (ie. with a <lt>img
src=image.pl<gt> HTML tag). The @data array should be set up the
same way as for the normal png method.
Graph.pm-style API
You might ask, "But what if I just want to add a few points to the
graph, and then display it, without all those references to
references?". Well, friend, the solution is simple. Borrowing the
add_pt idea from Matt Kruse's Graph module, you simply make a few calls
to the add_pt method, like so:
$obj->add_pt ('foo', 30, 25);
$obj->add_pt ('bar', 16, 32);
Or, if you want to be able to add entire datasets, simply use the
add_dataset method:
$obj->add_dataset ('foo', 'bar');
$obj->add_dataset (30, 16);
$obj->add_dataset (25, 32);
These methods check to make sure that the points and datasets you are
adding are the same size as the ones already there. So, if you have
two datasets currently stored, and try to add a data point with three
different values, it will carp (per the Carp module) an error message.
Similarly, if you try to add a dataset with 4 data points, and all the
other datasets have 3 data points, it will carp an error message.
Don't forget, when using this API, that I treat the first dataset as a
series of x-tick labels. So, in the above examples, the graph would
have two x-ticks, labeled 'foo' and 'bar', each with two data points.
Pie and ErrorBars handle it different, look at the documentation to see
how it works.
Adding a datafile
You can also add a complete datafile to a chart object. Just use
the add_datafile() method.
$obj->add_datafile('file', 'set' or 'pt');
file can be the name of the data file or a filehandle. 'set' or
'pt is the type of the datafile. If the parameter is 'set' then
each line in the data file has to be a complete data set. The value
of the set has to be separated by white spaces. For example the
file looks like this:
'foo' 'bar'
30 16
25 32
If the parameter is 'pt', one line has to include all values of one
data point separated by white spaces. For example:
'foo' 30 25
'bar' 16 32
Clearing the data
A simple call to the clear_data method empties any values that may
have been entered.
$obj->clear_data ();
Getting a copy of the data
If you want a copy of the data that has been added so far, make a
call to the get_data method like so:
$dataref = $obj->get_data;
It returns (you guessed it!) a reference to an array of references
to datasets. So the x-tick labels would be stored as
@x_labels = @{$dataref->[0]};
Sending the image to a file
If you just want to print this chart to a file, all you have to do
is pass the name of the file to the png() method.
$obj->png ("foo.png");
Sending the image to a filehandle
If you want to do something else with the image, you can also pass
a filehandle (either a typeglob or a FileHandle object) to png, and
it will print directly to that.
$obj->png ($filehandle);
$obj->png (FILEHANDLE);
CGI and Chart
Okay, so you're probably thinking (again), "Do I always have to
save these images to disk? What if I want to use Chart to create
dynamic images for my web site?" Well, here's the answer to that.
$obj->cgi_png ();
The cgi_png method will print the chart, along with the appropriate
http header, to stdout, allowing you to call chart-generating
scripts directly from your html pages (ie. with a <lt>img
src=image.pl<gt> HTML tag).
Produce a png image as a scalar
Like scalar_jpeg() the image is produced as a scalar so that the
programmer-user can do whatever the heck s/he wants to with it:
$obj-scalar_png($dataref)
Produce a jpeg image as a scalar
Like scalar_png() the image is produced as a scalar so that the
programmer-user can do whatever the heck s/he wants to with it:
$obj-scalar_jpeg($dataref)
Imagemap Support
Chart can also return the pixel positioning information so that you can
create image maps from the pngs Chart generates. Simply set the
'imagemap' option to 'true' before you generate the png, then call the
imagemap_dump() method afterwards to retrieve the information. You
will be returned a data structure almost identical to the @data array
described above to pass the data into Chart.
$imagemap_data = $obj->imagemap_dump ();
Instead of single data values, you will be passed references to arrays
of pixel information. For Bars, HorizontalBars and StackedBars charts,
the arrays will contain two x-y pairs (specifying the upper left and
lower right corner of the bar), like so
( $x1, $y1, $x2, $y2 ) = @{ $imagemap_data->[$dataset][$datapoint] };
For Lines, Points, ErrorBars, Split and LinesPoints, the arrays will
contain a single x-y pair (specifying the center of the point), like so
( $x, $y ) = @{ $imagemap_data->[$dataset][$datapoint] };
A few caveats apply here. First of all, GD treats the upper-left
corner of the png as the (0,0) point, so positive y values are measured
from the top of the png, not the bottom. Second, these values will
most likely contain long decimal values. GD, of course, has to
truncate these to single pixel values. Since I don't know how GD does
it, I can't truncate it the same way he does. In a worst-case
scenario, this will result in an error of one pixel on your imagemap.
If this is really an issue, your only option is to either experiment
with it, or to contact Lincoln Stein and ask him. Third, please
remember that the 0th dataset will be empty, since that's the place in
the @data array for the data point labels.
TO DO
ยท Add some 3-D graphs. Include True Type Fonts
BUGS
Probably quite a few, since it's been completely rewritten. As usual,
please mail me with any bugs, patches, suggestions, comments, flames,
death threats, etc.
AUTHOR
David Bonner (dbonner@cs.bu.edu)
MAINTAINERChart Group (Chart@fs.wettzell.de)
COPYRIGHTCopyright(c) 1997-1998 by David Bonner, 1999 by Peter Clark, 2001 by
the Chart group at BKG-Wettzell. All rights reserved. This program is
free software; you can redistribute it and/or modify it under the same
terms as Perl itself.
POD ERRORS
Hey! The above document had some coding errors, which are explained
below:
Around line 694:
'=item' outside of any '=over'
Around line 706:
'=item' outside of any '=over'
perl v5.18.1 2012-03-21 Chart(3)
