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https://github.com/pdlporters/pdl-graphics-simple

This is an interface layer to the several PDL::Graphics modules out there. It is intended to become part of the PDL core.
https://github.com/pdlporters/pdl-graphics-simple

gnuplot pdl perl pgplot plotting plplot prima

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This is an interface layer to the several PDL::Graphics modules out there. It is intended to become part of the PDL core.

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README 

        
=head1 OVERVIEW



PDL::Graphics::Simple is a unified plotting interface for PDL.  The

main distribution site is CPAN; the development repository is on

github.com.



=cut



=head1 NAME



PDL::Graphics::Simple - Simple backend-independent plotting for PDL



=head1 SYNOPSIS



 # Simple interface - throw plots up on-screen, ASAP

 use PDL::Graphics::Simple;

 imag $a;                     # Display an image PDL

 imag $a, 0, 300;             # Display with color range

 line $rrr, $fit;             # Plot a line



 points $rr, $sec;            # Plot points

 hold;                        # Hold graphics so subsequent calls overplot

 line $rrr, $fit;             # Overplot a line in a contrasting color

 release;                     # Release graphics



 # Object interface - simple plotting, to file or screen

 $w = pgswin( size=>[8,4], multi=>[2,2] ); # 2x2 plot grid on an 8"x4" window

 $w = pgswin( size=>[1000,1000,'px'], output=>'plot.png' ); # output to a PNG



 $w->plot( with=>'points', $rr, $sec, with=>'line', $rrr, $fit,

           {title=>"Points and fit", xlabel=>"Abscissa", ylabel=>"Ordinate"});



=head1 DESCRIPTION



PDL can plot through a plethora of external plotting modules.  Each

module tends to be less widely available than Perl itself, and to

require an additional step or two to install.  For simple applications

("throw up an image on the screen", or "plot a curve") it is useful to

have a subset of all plotting capability available in a backend-independent

layer.  PDL::Graphics::Simple provides that capability.



PDL::Graphics::Simple implements all the functionality used in the

PDL::Book examples, with identical syntax.  It also generalizes that

syntax - you can use ::Simple graphics, with slight syntactical

differences, in the same manner that you would use any of the engine

modules.  See the Examples below for details.



The plot you get will always be what you asked for, regardless of

which plotting engine you have installed on your system.



Only a small subset of PDL's complete graphics functionality is

supported -- each individual plotting module has unique advantages and

functionality that are beyond what PDL::Graphics::Simple can do.  Only

2-D plotting is supported.  For 3-D plotting, use

L or L directly.



When plotting to a file, the file output is not guaranteed to be

present until the plot object is destroyed (e.g. by being undefed or

going out of scope).



=head1 STATE OF DEVELOPMENT



PDL::Graphics::Simple currently supports most of the

planned functionality.  It is being released as a beta

test to determine if it meets users' needs and gain feedback on

the API -- so please give feedback!



=head1 SUPPORTED GRAPHICS ENGINES



PDL::Graphics::Simple includes support for the following graphics

engines.  Additional driver modules can be loaded dynamically; see

C, below.  Each of the engines has unique capabilities and

flavor that are not captured in PDL::Graphics::Simple - you are

encouraged to look at the individual modules for more capability!



=over 3



=item * Gnuplot (via PDL::Graphics::Gnuplot)



Gnuplot is an extremely richly featured plotting package that offers

markup, rich text control, RGB color, and 2-D and 3-D plotting.  Its

output is publication quality.  It is supported on POSIX systems,

MacOS, and Microsoft Windows, and is available from most package

managers.



=item * PGPLOT  (via PDL::Graphics::PGPLOT::Window)



PGPLOT is venerable and nearly as fully featured as Gnuplot for 2-D

plotting.  It lacks RGB color output. It does have rich text control,

but uses simple plotter fonts that are generated internally.  It

is supported on MacOS and POSIX, but is not as widely available as

Gnuplot.



=item * PLplot (via PDL::Graphics::PLplot)



PLplot is a moderately full featured plotting package that

generates publication quality output with a simple high-level interface.

It is supported on MacOS and POSIX.



=item * Prima (via PDL::Graphics::Prima)



Prima is based around a widget paradigm that enables complex

interaction with data in real-time, and it is highly optimized for

that application.  It is not as mature as the other platforms,

particularly for static plot generation to files.  This means that

PDL::Graphics::Simple does not play to its considerable strengths,

although Prima is serviceable and fast in this application.  Please

run the Prima demo in the perldl shell for a better sample of Prima's

capabilities.



=back



=head1 EXAMPLES



PDL::Graphics::Simple can be called using plot-atomic or curve-atomic

plotting styles, using a pidgin form of calls to any of the main

modules.  The examples are divided into Book-like (very simple),

PGPLOT-like (curve-atomic), and Gnuplot-like (plot-atomic) cases.



There are three main styles of interaction with plot objects that

PDL::Graphics::Simple supports, reflective of the pre-existing

modules' styles of interaction.  You can mix-and-match them to match

your particular needs and coding style.  Here are examples showing

convenient ways to call the code.



=head2 First steps (non-object-oriented)



For the very simplest actions there are non-object-oriented shortcuts.

Here are some examples of simple tasks, including axis labels and plot

titles.  These non-object-oriented shortcuts are useful for display

with the default window size.  They make use of a package-global plot

object.



The non-object interface will keep using the last plot engine you used

successfully.  On first start, you can specify an engine with the

environment variable C. As of 1.011, only that will be tried, but

if you didn't specify one, all known engines are tried in alphabetical

order until one works.



The value of C should be the "shortname" of the

engine, currently:



=over



=item C



=item C



=item C



=item C



=back



=over 3



=item * Load module and create line plots



 use PDL::Graphics::Simple;

 $x = xvals(51)/5;

 $y = $x**3;



 $y->line;

 line( $x, $y );

 line( $x, $y, {title=>"My plot", ylabel=> "Ordinate", xlabel=>"Abscissa"} );



=item * Bin plots



 $y->bins;

 bins($y, {title=>"Bin plot", xl=>"Bin number", yl=>"Count"} );



=item * Point plots



 $y->points;

 points($y, {title=>"Points plot"});



=item * Logarithmic scaling



 line( $y, { log=>'y' } );    # semilog

 line( $y, { log=>'xy' } );   # log-log



=item * Image display



 $im = 10 * sin(rvals(101,101)) / (10 + rvals(101,101));

 imag $im;          # Display image

 imag $im, 0, 1;    # Set lower/upper color range



=item * Overlays



 points($x, $y, {logx=>1});

 hold;

 line($x, sqrt($y)*10);

 release;



=item * Justify aspect ratio



 imag $im, {justify=>1}

 points($x, $y, {justify=>1});



=item * Erase/delete the plot window



 erase();



=back



=head2 Simple object-oriented plotting



More functionality is accessible through direct use of the PDL::Graphics::Simple

object.  You can set plot size, direct plots to files, and set up multi-panel plots.



The constructor accepts window configuration options that set the plotting

environment, including size, driving plot engine, output, and multiple

panels in a single window.



For interactive/display plots, the plot is rendered immediately, and lasts until

the object is destroyed.  For file plots, the file is not guaranteed to exist

and be correct until the object is destroyed.



The basic plotting method is C.  C accepts a collection of

arguments that describe one or more "curves" (or datasets) to plot,

followed by an optional plot option hash that affects the entire plot.

Overplotting is implemented via plot option, via a held/released state

(as in PGPLOT), and via a convenience method C that causes the

current plot to be overplotted on the previous one.



Plot style (line/points/bins/etc.) is selected via the C curve option.

Several convenience methods exist to create plots in the various styles.



=over 3



=item * Load module and create basic objects



 use PDL::Graphics::Simple;

 $x = xvals(51)/5;

 $y = $x**3;



 $win = pgswin();                       # plot to a default-shape window

 $win = pgswin( size=>[4,3] );          # size is given in inches by default

 $win = pgswin( size=>[10,5,'cm'] );    # You can feed in other units too

 $win = pgswin( out=>'plot.ps' );       # Plot to a file (type is via suffix)

 $win = pgswin( engine=>'gnuplot' );    # Pick a particular plotting engine

 $win = pgswin( multi=>[2,2] );         # Set up for a 2x2 4-panel plot



=item * Simple plots with C



 $win->plot( with=>'line', $x, $y, {title=>"Simple line plot"} );

 $win->plot( with=>'errorbars', $x, $y, sqrt($y), {title=>"Error bars"} );

 $win->plot( with=>'circles', $x, $y, sin($x)**2 );



=item * Plot overlays



 # All at once

 $win->plot( with=>'line', $x, $y,   with=>'circles', $x, $y/2, sqrt($y)  );



 # Using oplot (IDL-style; PLplot-style)

 $win->plot(  with=>'line', $x, $y );

 $win->oplot( with=>'circles', $x, $y/2, sqrt($y) );



 # Using object state (PGPLOT-style)

 $win->line(  $x, $y );

 $win->hold;

 $win->circles( $x, $y/2, sqrt($y) );

 $win->release;



=back



=head1 FUNCTIONS



=cut

=head2 show



=for usage



 PDL::Graphics::Simple::show



=for ref



C lists the supported engines and a one-line synopsis of each.



=cut

=head2 pgswin - exported constructor



=for usage



 $w = pgswin( %opts );



=for ref



C is a constructor that is exported by default into the using package. Calling

C is exactly the same as calling C<< PDL::Graphics::Simple->new(%opts) >>.



=head2 new



=for usage



 $w = PDL::Graphics::Simple->new( %opts );



=for ref



C is the main constructor for PDL::Graphics::Simple.  It accepts a list of options

about the type of window you want:



=over 3



=item engine



If specified, this must be one of the supported plotting engines.  You

can use a module name or the shortened name.  If you don't give one,

the constructor will try the last one you used, or else scan through

existing modules and pick one that seems to work.  It will first check

the environment variable C, and as of 1.011, only that will be tried, but

if you didn't specify one, all known engines are tried in alphabetical

order until one works.



=item size



This is a window size as an ARRAY ref containing [width, height,

units].  If no units are specified, the default is "inches".  Accepted

units are "in","pt","px","mm", and "cm". The conversion used for pixels

is 100 px/inch.



=item type



This describes the kind of plot to create, and should be either "file"

or "interactive" - though only the leading character is checked.  If

you don't specify either C or C (below), the default is

"interactive". If you specify only C, the default is "file".



=item output



This should be a window number or name for interactive plots, or a

file name for file plots.  The default file name is "plot.png" in the

current working directory.  Individual plotting modules all support at

least '.png', '.pdf', and '.ps' -- via format conversion if necessary.

Most other standard file types are supported but are not guaranteed to

work.



=item multi



This enables plotting multiple plots on a single screen.  You feed in

a single array ref containing (nx, ny).  Subsequent calls to plot

send graphics to subsequent locations on the window.  The ordering

is always horizontal first, and left-to-right, top-to-bottom.



=back



=cut

=head2 plot



=for usage



 $w = PDL::Graphics::Simple->new( %opts );

 $w->plot($data);



=for ref



C plots zero or more traces of data on a graph.  It accepts two kinds of

options: plot options that affect the whole plot, and curve options

that affect each curve.  The arguments are divided into "curve blocks", each

of which contains a curve options hash followed by data.



If the last argument is a hash ref, it is always treated as plot options.

If the first and second arguments are both hash refs, then the first argument

is treated as plot options and the second as curve options for the first curve

block.



=head3 Plot options:



=over 3



=item oplot



If this is set, then the plot overplots a previous plot.



=item title



If this is set, it is a title for the plot as a whole.



=item xlabel



If this is set, it is a title for the X axis.



=item ylabel



If this is set, it is a title for the Y axis.



=item xrange



If this is set, it is a two-element ARRAY ref containing a range for

the X axis.  If it is clear, the axis is autoscaled.



=item yrange



If this is set, it is a two-element ARRAY ref containing a range for

the Y axis.  If it is clear, the axis is autoscaled.



=item logaxis



This should be empty, "x", "y", or "xy" (case and order insensitive).

Named axes are scaled logarithmically.



=item crange



If this is set, it is a two-element ARRAY ref containing a range for

color values, full black to full white.  If it is clear, the engine or

plot module is responsible for setting the range.



=item wedge



If this is set, then image plots get a scientific colorbar on the

right side of the plot.  (You can also say "colorbar", "colorbox", or "cb" if

you're more familiar with Gnuplot).



=item justify



If this is set to a true value, then the screen aspect ratio is adjusted

to keep the Y axis and X axis scales equal -- so circles appear circular, and

squares appear square.



=item legend (EXPERIMENTAL)



The "legend" plot option is intended for full support but it is currently

experimental:  it is not fully implemented in all the engines, and

implementation is more variable than one would like in the engines that

do support it.



This controls whether and where a plot legend should be placed.  If

you set it, you supply a combination of 't','b','c','l', and 'r':

indicating top, bottom, center, left, right position for the plot

legend.  For example, 'tl' for top left, 'tc' for center top, 'c' or

'cc' for dead center.  If left unset, no legend will be plotted.  If

you set it but don't specify a position (or part of one), it defaults

to top and left.



If you supply even one 'key' curve option in the curves, legend defaults

to the value 'tl' if it isn't specified.



=back



=head3 Curve options:



=over 3



=item with



This names the type of curve to be plotted.  See below for supported curve types.



=item key



This gives a name for the following curve, to be placed in a master plot legend.

If you don't specify a name but do call for a legend, the curve will be named

with the plot type and number (e.g. "line 3" or "points 4").



=item width



This lets you specify the width of the line, as a multiplier on the standard

width the engine uses.  That lets you pick normal-width or extra-bold lines

for any given curve.  The option takes a single positive natural number.



=item style



You can specify the line style in a very limited way -- as a style

number supported by the backend.  The styles are generally defined by

a mix of color and dash pattern, but the particular color and dash

pattern depend on the engine in use. The first 30 styles are

guaranteed to be distinguishable. This is useful to produce, e.g.,

multiple traces with the same style. C<0> is a valid value.



=back



=head3 Curve types supported



=over 3



=item points



This is a simple point plot.  It takes 1 or 2 columns of data.



=item lines



This is a simple line plot. It takes 1 or 2 columns of data.



=item bins



Stepwise line plot, with the steps centered on each X value.  1 or 2 columns.



=item errorbars



Simple points-with-errorbar plot, with centered errorbars.  It takes 2

or 3 columns, and the last column is the absolute size of the errorbar (which

is centered on the data point).



=item limitbars



Simple points-with-errorbar plot, with asymmetric errorbars.  It takes

3 or 4 columns, and the last two columns are the absolute low and high

values of the errorbar around each point (specified relative to the

origin, not relative to the data point value).



=item circles



Plot unfilled circles.  Requires 2 or 3 columns of data; the last

column is the radius of each circle.  The circles are circular in

scientific coordinates, not necessarily in screen coordinates (unless

you specify the "justify" plot option).



=item image



This is a monochrome or RGB image.  It takes a 2-D or 3-D array of

values, as (width x height x color-index).  Images are displayed in

a sepiatone color scale that enhances contrast and preserves intensity

when converted to grayscale.  If you use the convenience routines

(C or C), the "justify" plot option defaults to 1 -- so

the image will be displayed with square pixel aspect.  If you use

C<< plot(with=>'image' ...) >>, "justify" defaults to 0 and you will have

to set it if you want square pixels.



For RGB images, the numerical values need to be in the range 0-255,

as they are interpreted as 8 bits per plane colour values. E.g.:



  $w = pgswin(); # plot to a default-shape window

  $w->image( pdl(xvals(9,9),yvals(9,9),rvals(9,9))*20 );



  # or, from an image on disk:

  $image_data = rpic( 'my-image.png' )->mv(0,-1); # need RGB 3-dim last

  $w->image( $image_data );



If you have a 2-D field of values that you would like to see with a heatmap:



  use PDL::Graphics::ColorSpace;

  sub as_heatmap {

    my ($d) = @_;

    my $max = $d->max;

    die "as_heatmap: can't work if max == 0" if $max == 0;

    $d /= $max; # negative OK

    my $hue   = (1 - $d)*240;

    $d = cat($hue, pdl(1), pdl(1));

    (hsv_to_rgb($d->mv(-1,0)) * 255)->byte->mv(0,-1);

  }

  $w->image( as_heatmap(rvals 300,300) );



=item contours



As of 1.012. Draws contours. Takes a 2-D array of values, as (width x

height), and optionally a 1-D vector of contour values.



=item fits



As of 1.012. Displays an image from an ndarray with a FITS header.

Uses C etc to make X & Y axes including labels.



=item polylines



As of 1.012. Draws polylines, with 2 arguments (C<$xy>, C<$pen>).

The "pen" has value 0 for the last point in that polyline.



  use PDL::Transform::Cartography;

  use PDL::Graphics::Simple qw(pgswin);

  $coast = earth_coast()->glue( 1, scalar graticule(15,1) );

  $w = pgswin();

  $w->plot(with => 'polylines', $coast->clean_lines);



=item labels



This places text annotations on the plot.  It requires three input

arguments: the X and Y location(s) as PDLs, and the label(s) as a list

ref.  The labels are normally left-justified, but you can explicitly

set the alignment for each one by beginning the label with "<" for

left "|" for center, and ">" for right justification, or a single " "

to denote default justification (left).



=back



=cut

=head2 oplot



=for usage



 $w = PDL::Graphics::Simple->new( %opts );

 $w->plot($data);

 $w->oplot($more_data);



=for ref



C is a convenience interface.  It is exactly

equivalent to C except it sets the plot option C,

so that the plot will be overlain on the previous one.



=cut

=head2 line, points, image, imag, cont



=for usage



 # Object-oriented convenience

 $w = PDL::Graphics::Simple->new( % opts );

 $w->line($data);



 # Very Lazy Convenience

 $a = xvals(50);

 lines $a;

 $im = sin(rvals(100,100)/3);

 imag $im;

 imag $im, 0, 1, {title=>"Bullseye?", j=>1};



=for ref



C, C, and C are convenience

interfaces.  They are exactly equivalent to C except that

they set the default "with" curve option to the appropriate

plot type.



C is even more DWIMMy for PGPLOT users or PDL Book readers:

it accepts up to three non-hash arguments at the start of the

argument list.  The second and third are taken to be values for

the C plot option.



C resembles the PGPLOT function.



=cut

=head2 erase



=for usage



 use PDL::Graphics::Simple qw/erase hold release/;

 line xvals(10), xvals(10)**2 ;

 sleep 5;

 erase;



=for ref



C removes a global plot window.  It should not be called as a method.

To remove a plot window contained in a variable, undefine it.



=cut

=head2 hold



=for usage



 use PDL::Graphics::Simple;

 line xvals(10);

 hold;

 line xvals(10)**0.5;



=for ref



Causes subsequent plots to be overplotted on any existing one.  Called

as a function with no arguments, C applies to the global object.

Called as an object method, it applies to the object.



=cut

=head2 release



=for usage



 use PDL::Graphics::Simple;

 line xvals(10);

 hold;

 line xvals(10)**0.5;

 release;

 line xvals(10)**0.5;



=for ref



Releases a hold placed by C.



=cut

=head2 register



=for usage



 PDL::Graphics::Simple::register( \%description );



=for ref



This is the registration mechanism for new driver methods for

C.  Compliant drivers should announce

themselves at compile time by calling C, passing

a hash ref containing the following keys:



=over



=item shortname



This is the short name of the engine, by which users refer to it colloquially.



=item module



This is the fully qualified package name of the module itself.



=item engine



This is the fully qualified package name of the Perl API for the graphics engine.



=item synopsis



This is a brief string describing the backend



=item pgs_api_version



This is a one-period version number of PDL::Graphics::Simple against which

the module has been tested.  A warning will be thrown if the version isn't the

same as C<$PDL::Graphics::Simple::API_VERSION>.



That value will only change when the API changes, allowing the modules

to be released independently, rather than with every version of

PDL::Graphics::Simple as up to 1.010.



=back



=cut

=head1 IMPLEMENTATION



PDL::Graphics::Simple defines an object that represents a plotting

window/interface.  When you construct the object, you can either

specify a backend or allow PDL::Graphics::Simple to find a backend

that seems to work on your system.  Subsequent plotting commands are

translated and passed through to that working plotting module.



PDL::Graphics::Simple calls are dispatched in a two-step process. The

main module curries the arguments, parsing them into a regularized

form and carrying out DWIM optimizations. The regularized arguments

are passed to implementation classes that translate them into the APIs of their

respective plot engines.  The classes are very simple and implement

only a few methods, outlined below.  They are intended only to be

called by the PDL::Graphics::Simple driver, which limits the need for

argument processing, currying, and parsing. The classes are thus

responsible only for converting the regularized parameters to plot

calls in the form expected by their corresponding plot modules.



PDL::Graphics::Simple works through a call-and-dispatch system rather

than taking full advantage of inheritance.  That is for two reasons:

(1) it makes central control mildly easier going forward, since calls

are dispatched through the main module; and (2) it makes the

non-object-oriented interface easier to implement since the main

interface modules are in one place and can access the global object

easily.



=head2 Interface class methods



Each interface module supports the following methods:



=cut

=head3 check



C attempts to load the relevant engine module and test that it

is working.  In addition to returning a boolean value indicating

success if true, it registers its success or failure in

the main $mods hash, under the "ok" flag.  If there is a failure that

generates an error message, the error is logged under the "msg" flag.



C accepts one parameter, "force".  If it is missing or false,

and "ok" is defined, check just echoes the prior result.  If it is

true, then check actually checks the status regardless of the "ok"

flag.



=head3 new



C creates and returns an appropriate plot object, or dies on

failure.



Each C method should accept the following options, defined as in

the description for PDL::Graphics::Simple::new (above).  There is

no need to set default values as all arguments should be set to

reasonable values by the superclass.



For file output, the method should autodetect file type by dot-suffix.

At least ".png" and ".ps" should be supported.



Required options: C, C, C, C.



=head3 plot



C generates a plot.  It should accept a standardized collection

of options as generated by the PDL::Graphics::Simple plot method:

standard plot options as a hash ref, followed by a list of curve

blocks.  It should render either a full-sized plot that fills the plot

window or, if the object C option was set on construction, the

current subwindow.  For interactive plot types it should act as an

atomic plot operation, displaying the complete plot.  For file plot

types the atomicity is not well defined, since multiplot grids may

be problematic, but the plot should be closed as soon as practical.



The plot options hash contains the plot options listed under C,

above, plus one additional flag - C - that indicates the new

data is to be overplotted on top of whatever is already present in the

plotting window.  All options are present in the hash. The C,

C, C, and C options default to undef, which

indicates the corresponding plot feature should not be rendered.  The

C, C, C, C, C, and C

parameters are always both present and defined.



If the C plot option is set, then the plot should be overlain on

a previous plot - otherwise the module should display a fresh plot.



Each curve block consists of an ARRAY ref with a hash in the 0 element

and all required data in the following elements, one PDL per

(ordinate/abscissa).  For 1-D plot types (like points and lines) the

PDLs must be 1D.  For image plot types the lone PDL must be 2D

(monochrome) or 3D(RGB).



The hash in the curve block contains the curve options for that

particular curve.  They are all set to have reasonable default values.

The values passed in are C and C.  If the C

option is undefined, then the curve should not be placed into a plot

legend (if present).



=head1 ENVIRONMENT



Setting some environment variables affects operation of the module:



=head2 PDL_SIMPLE_ENGINE



See L.



=head2 PDL_SIMPLE_DEVICE



If this is a meaningful thing for the given engine, this value will be

used instead of the driver module guessing.



=head2 PDL_SIMPLE_OUTPUT



Overrides passed-in arguments, to create the given file as output.

If it contains C<%d>, then with Gnuplot that will be replaced with an

increasing number (an amazing L feature).



=head1 TO-DO



Deal with legend generation.  In particular: adding legends with multi-call

protocols is awkward and leads to many edge cases in the internal protocol.

This needs more thought.



=head1 REPOSITORY



L



=head1 AUTHOR



Craig DeForest, C<<  >>



=head1 LICENSE AND COPYRIGHT



Copyright 2013 Craig DeForest



This program is free software; you can redistribute it and/or modify

it under the terms of either: the Gnu General Public License v2 as

published by the Free Software Foundation; or the Perl Artistic

License included with the Perl language.



see http://dev.perl.org/licenses/ for more information.



=cut