NAME

PDL::Graphics::PLplot - Object-oriented interface from perl/PDL to the PLPLOT plotting library

SYNOPSIS

use PDL;
use PDL::Graphics::PLplot;

my $pl = PDL::Graphics::PLplot->new (DEV => "png", FILE => "test.png");
my $x  = sequence(10);
my $y  = $x**2;
$pl->xyplot($x, $y);
$pl->close;

For more information on PLplot, see

http://www.plplot.org/

Also see the test file, t/plplot.pl in this distribution for some working examples.

DESCRIPTION

This is the PDL interface to the PLplot graphics library. It is designed to be simple and light weight with a familiar 'perlish' Object Oriented interface.

OPTIONS

The following options are supported. Most options can be used with any function. A few are only supported on the call to 'new'.

Options used upon creation of a PLplot object (with 'new'):

BACKGROUND

Set the color for index 0, the plot background

DEV

Set the output device type. To see a list of allowed types, try:

PDL::Graphics::PLplot->new();

PDL::Graphics::PLplot->new(DEV => 'png', FILE => 'test.png');

FILE

Set the output file or display. For file output devices, sets the output file name. For graphical displays (like 'xwin') sets the name of the display, eg ('hostname.foobar.com:0')

PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png');
PDL::Graphics::PLplot->new(DEV => 'xwin', FILE => ':0');

OPTS

Set plotting options. See the PLplot documentation for the complete listing of available options. The value of 'OPTS' must be a hash reference, whose keys are the names of the options. For instance, to obtain PostScript fonts with the ps output device, use:

PDL::Graphics::PLplot->new(DEV => 'ps', OPTS => {drvopt => 'text=1'});

MEM

This option is used in conjunction with DEV => 'mem'. This option takes as input a PDL image and allows one to 'decorate' it using PLplot. The 'decorated' PDL image can then be written to an image file using, for example, PDL::IO::Pic. This option may not be available if plplot does not include the 'mem' driver.

# read in Earth image and draw an equator.
my $pl = PDL::Graphics::PLplot->new (MEM => $earth, DEV => 'mem');
my $x  = pdl(-180, 180);
my $y  = zeroes(2);
$pl->xyplot($x, $y,
            BOX => [-180,180,-90,90],
            VIEWPORT => [0.0, 1.0, 0.0, 1.0],
            XBOX => '', YBOX => '',
            PLOTTYPE => 'LINE');
$pl->close;

FRAMECOLOR

Set color index 1, the frame color

JUST

A flag used to specify equal scale on the axes. If this is not specified, the default is to scale the axes to fit best on the page.

PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png', JUST => 1);

ORIENTATION

The orientation of the plot:

0 --   0 degrees (landscape mode)
1 --  90 degrees (portrait mode)
2 -- 180 degrees (seascape mode)
3 -- 270 degrees (upside-down mode)

Intermediate values (0.2) are acceptable if you are feeling daring.

# portrait orientation
PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png', ORIENTATION => 1);

PAGESIZE

Set the size in pixels of the output page.

# PNG 500 by 600 pixels
PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png', PAGESIZE => [500,600]);

SUBPAGES

Set the number of sub pages in the plot, [$nx, $ny]

# PNG 300 by 600 pixels
# Two subpages stacked on top of one another.
PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png', PAGESIZE => [300,600],
                                            SUBPAGES => [1,2]);

Options used after initialization (after 'new')

BOX

Set the plotting box in world coordinates. Used to explicitly set the size of the plotting area.

my $pl = PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png');
$pl->xyplot ($x, $y, BOX => [0,100,0,200]);

CHARSIZE

Set the size of text in multiples of the default size. CHARSIZE => 1.5 gives characters 1.5 times the normal size.

COLOR

Set the current color for plotting and character drawing. Colors are specified not as color indices but as RGB triples. Some pre-defined triples are included:

BLACK        GREEN        WHEAT        BLUE
RED          AQUAMARINE   GREY         BLUEVIOLET
YELLOW       PINK         BROWN        CYAN
TURQUOISE    MAGENTA      SALMON       WHITE
ROYALBLUE    DEEPSKYBLUE  VIOLET       STEELBLUE1
DEEPPINK     MAGENTA      DARKORCHID1  PALEVIOLETRED2
TURQUOISE1   LIGHTSEAGREEN SKYBLUE     FORESTGREEN
CHARTREUSE3  GOLD2        SIENNA1      CORAL
HOTPINK      LIGHTCORAL   LIGHTPINK1   LIGHTGOLDENROD

# These two are equivalent:
$pl->xyplot ($x, $y, COLOR => 'YELLOW');
$pl->xyplot ($x, $y, COLOR => [0,255,0]);

LINEWIDTH

Set the line width for plotting. Values range from 1 to a device dependent maximum.

LINESTYLE

Set the line style for plotting. Pre-defined line styles use values 1 to 8, one being a solid line, 2-8 being various dashed patterns.

MAJTICKSIZE

Set the length of major ticks as a fraction of the default setting. One (default) means leave these ticks the normal size.

MINTICKSIZE

Set the length of minor ticks (and error bar terminals) as a fraction of the default setting. One (default) means leave these ticks the normal size.

NXSUB

The number of minor tick marks between each major tick mark on the X axis. Specify zero (default) to let PLplot compute this automatically.

NYSUB

The number of minor tick marks between each major tick mark on the Y axis. Specify zero (default) to let PLplot compute this automatically.

PALETTE

Load pre-defined color map 1 color ranges. Currently, values include:

RAINBOW   -- from Red to Violet through the spectrum
REVERSERAINBOW   -- Violet through Red
GREYSCALE -- from black to white via grey.
REVERSEGREYSCALE -- from white to black via grey.
GREENRED  -- from green to red
REDGREEN  -- from red to green

# Plot x/y points with the z axis in color
$pl->xyplot ($x, $y, PALETTE => 'RAINBOW', PLOTTYPE => 'POINTS', COLORMAP => $z);

PLOTTYPE

Specify which type of XY plot is desired:

LINE       -- A line
POINTS     -- A bunch of symbols
LINEPOINTS -- both

SUBPAGE

Set which subpage to plot on. Subpages are numbered 1 to N. A zero can be specified meaning 'advance to the next subpage' (just a call to pladv()).

my $pl = PDL::Graphics::PLplot->new(DEV      => 'png',
                                      FILE     => 'test.png',
                                      SUBPAGES => [1,2]);
$pl->xyplot ($x, $y, SUBPAGE => 1);
$pl->xyplot ($a, $b, SUBPAGE => 2);

SYMBOL

Specify which symbol to use when plotting PLOTTYPE => 'POINTS'. A large variety of symbols are available, see: http://plplot.sourceforge.net/examples-data/demo07/x07.*.png, where * is 01 - 17.

SYMBOLSIZE

Specify the size of symbols plotted in multiples of the default size (1). Value are real numbers from 0 to large.

TEXTPOSITION

Specify the placement of text. Either relative to border, specified as:

[$side, $disp, $pos, $just]

Where

side = 't', 'b', 'l', or 'r' for top, bottom, left and right
disp is the number of character heights out from the edge
pos  is the position along the edge of the viewport, from 0 to 1.
just tells where the reference point of the string is: 0 = left, 1 = right, 0.5 = center.

or inside the plot window, specified as:

[$x, $y, $dx, $dy, $just]

Where

x  = x coordinate of reference point of string.
y  = y coordinate of reference point of string.
dx   Together with dy, this specifies the inclination of the string.
     The baseline of the string is parallel to a line joining (x, y) to (x+dx, y+dy).
dy   Together with dx, this specifies the inclination of the string.
just Specifies the position of the string relative to its reference point.
     If just=0, the reference point is at the left and if just=1,
     it is at the right of the string. Other values of just give
     intermediate justifications.

# Plot text on top of plot
$pl->text ("Top label",  TEXTPOSITION => ['t', 4.0, 0.5, 0.5]);

# Plot text in plotting area
$pl->text ("Line label", TEXTPOSITION => [50, 60, 5, 5, 0.5]);

TITLE

Add a title on top of a plot.

# Plot text on top of plot
$pl->xyplot ($x, $y, TITLE => 'X vs. Y');

VIEWPORT

Set the location of the plotting window on the page. Takes a four element array ref specifying:

xmin -- The coordinate of the left-hand edge of the viewport. (0 to 1)
xmax -- The coordinate of the right-hand edge of the viewport. (0 to 1)
ymin -- The coordinate of the bottom edge of the viewport. (0 to 1)
ymax -- The coordinate of the top edge of the viewport. (0 to 1)

# Make a small plotting window in the lower left of the page
$pl->xyplot ($x, $y, VIEWPORT => [0.1, 0.5, 0.1, 0.5]);

# Also useful in creating color keys:
$pl->xyplot   ($x, $y, PALETTE => 'RAINBOW', PLOTTYPE => 'POINTS', COLORMAP => $z);
$pl->colorkey ($z, 'v', VIEWPORT => [0.93, 0.96, 0.15, 0.85]);

XBOX

Specify how to label the X axis of the plot as a string of option letters:

a: Draws axis, X-axis is horizontal line (y=0), and Y-axis is vertical line (x=0).
b: Draws bottom (X) or left (Y) edge of frame.
c: Draws top (X) or right (Y) edge of frame.
f: Always use fixed point numeric labels.
g: Draws a grid at the major tick interval.
h: Draws a grid at the minor tick interval.
i: Inverts tick marks, so they are drawn outwards, rather than inwards.
l: Labels axis logarithmically. This only affects the labels, not the data,
   and so it is necessary to compute the logarithms of data points before
   passing them to any of the drawing routines.
m: Writes numeric labels at major tick intervals in the
   unconventional location (above box for X, right of box for Y).
n: Writes numeric labels at major tick intervals in the conventional location
   (below box for X, left of box for Y).
s: Enables subticks between major ticks, only valid if t is also specified.
t: Draws major ticks.

The default is 'BCNST' which draws lines around the plot, draws major and minor ticks and labels major ticks.

 # plot two lines in a box with independent X axes labeled
 # differently on top and bottom
 $pl->xyplot($x1, $y, XBOX  => 'bnst',  # bottom line, bottom numbers, ticks, subticks
	              YBOX  => 'bnst'); # left line, left numbers, ticks, subticks
 $pl->xyplot($x2, $y, XBOX => 'cmst', # top line, top numbers, ticks, subticks
	              YBOX => 'cst',  # right line, ticks, subticks
	              BOX => [$x2->minmax, $y->minmax]);

XERRORBAR

Used only with "xyplot". Draws horizontal error bars at all points ($x, $y) in the plot. Specify a PDL containing the same number of points as $x and $y which specifies the width of the error bar, which will be centered at ($x, $y).

XLAB

Specify a label for the X axis.

XTICK

Interval (in graph units/world coordinates) between major x axis tick marks. Specify zero (default) to allow PLplot to compute this automatically.

YBOX

Specify how to label the Y axis of the plot as a string of option letters. See "XBOX".

YERRORBAR

Used only for xyplot. Draws vertical error bars at all points ($x, $y) in the plot. Specify a PDL containing the same number of points as $x and $y which specifies the width of the error bar, which will be centered at ($x, $y).

YLAB

Specify a label for the Y axis.

YTICK

Interval (in graph units/world coordinates) between major y axis tick marks. Specify zero (default) to allow PLplot to compute this automatically.

ZRANGE

For "xyplot" (when COLORMAP is specified), for "shadeplot" and for "colorkey". Normally, the range of the Z variable (color) is taken as $z->minmax. If a different range is desired, specify it in ZRANGE, like so:

$pl->shadeplot ($z, $nlevels, PALETTE => 'GREENRED', ZRANGE => [0,100]);

  $pl->xyplot ($x, $y, PALETTE  => 'RAINBOW', PLOTTYPE => 'POINTS',
	               COLORMAP => $z,        ZRANGE => [-90,-20]);
  $pl->colorkey  ($z, 'v', VIEWPORT => [0.93, 0.96, 0.13, 0.85],
                       ZRANGE => [-90,-20]);

FUNCTIONS

new

Create an object representing a plot.

Arguments:
none.

Supported options:
BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

my $pl = PDL::Graphics::PLplot->new(DEV => 'png',  FILE => 'test.png');

setparm

Set options for a plot object.

Arguments:
none.

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

$pl->setparm (TEXTSIZE => 2);

xyplot

Plot XY lines and/or points. Also supports color scales for points. This function works with bad values. If a bad value is specified for a points plot, it is omitted. If a bad value is specified for a line plot, the bad value makes a gap in the line. This is useful for drawing maps; for example $x and $y can be the continent boundary latitude and longitude.

Arguments:
$x, $y

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

$pl->xyplot($x, $y, PLOTTYPE => 'POINTS', COLOR => 'BLUEVIOLET', SYMBOL => 1, SYMBOLSIZE => 4);
$pl->xyplot($x, $y, PLOTTYPE => 'LINEPOINTS', COLOR => [50,230,30]);
$pl->xyplot($x, $y, PALETTE => 'RAINBOW', PLOTTYPE => 'POINTS', COLORMAP => $z);

stripplots

Plot a set of strip plots with a common X axis, but with different Y axes. Looks like a stack of long, thin XY plots, all line up on the same X axis.

Arguments:
$x  -- 1D PDL with common X axis values, length = N
$ys -- 2D PDL with M Y-axis values: N x M
%opts -- Options hash

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

my $x  = sequence(20);
my $y1  = $x**2;
my $y2  = sqrt($x);
my $y3  = $x**3;
my $y4  = sin(($x/20) * 2 * $pi);
$ys  = cat($y1, $y2, $y3, $y4);
$pl->stripplots($x, $ys, PLOTTYPE => 'LINE', TITLE => 'functions',
                         YLAB     => ['x**2', 'sqrt(x)', 'x**3', 'sin(x/20*2pi)'],
                         COLOR    => ['GREEN', 'DEEPSKYBLUE', 'DARKORCHID1', 'DEEPPINK'], XLAB => 'X label');

In addition, COLOR may be specified as a reference to a list of colors.  If
this is done, the colors are applied separately to each plot.

Also, the options Y_BASE and Y_GUTTER can be specified.  Y_BASE gives the Y offset
of the bottom of the lowest plot (0-1, specified like a VIEWPORT, defaults to 0.1) and Y_GUTTER
gives the gap between the graphs (0-1, default = 0.02).

colorkey

Plot a color key showing which color represents which value

Arguments:
$range   : A PDL which tells the range of the color values
$orientation : 'v' for vertical color key, 'h' for horizontal

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

# Plot X vs. Y with Z shown by the color.  Then plot
# vertical key to the right of the original plot.
$pl->xyplot ($x, $y, PALETTE => 'RAINBOW', PLOTTYPE => 'POINTS', COLORMAP => $z);
$pl->colorkey ($z, 'v', VIEWPORT => [0.93, 0.96, 0.15, 0.85]);

shadeplot

Create a shaded contour plot of 2D PDL 'z' with 'nsteps' contour levels. Linear scaling is used to map the coordinates of Z(X, Y) to world coordinates via the "BOX" option.

Arguments:
$z : A 2D PDL which contains surface values at each XY coordinate.
$nsteps : The number of contour levels requested for the plot.

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

# vertical key to the right of the original plot.
# The BOX must be specified to give real coordinate values to the $z array.
$pl->shadeplot ($z, $nsteps, BOX => [-1, 1, -1, 1], PALETTE => 'RAINBOW', ZRANGE => [0,100]);
$pl->colorkey  ($z, 'v', VIEWPORT => [0.93, 0.96, 0.15, 0.85], ZRANGE => [0,100]);

histogram

Create a histogram of a 1-D variable.

Arguments:
$x : A 1D PDL
$nbins : The number of bins to use in the histogram.

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

$pl->histogram ($x, $nbins, BOX => [$min, $max, 0, 100]);

bargraph

Simple utility to plot a bar chart with labels on the X axis. The usual options can be specified, plus one other: MAXBARLABELS specifies the maximum number of labels to allow on the X axis. The default is 20. If this value is exceeded, then every other label is plotted. If twice MAXBARLABELS is exceeded, then only every third label is printed, and so on.

Arguments:
$labels -- A reference to a perl list of strings.
$values -- A PDL of values to be plotted.

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

$labels = ['one', 'two', 'three'];
$values = pdl(1, 2, 3);

# Note if TEXTPOSITION is specified, it must be in 4 argument mode (border mode):
# [$side, $disp, $pos, $just]
#
# Where side = 't', 'b', 'l', or 'r' for top, bottom, left and right
#              'tv', 'bv', 'lv' or 'rv' for top, bottom, left or right perpendicular to the axis.
#
#     disp is the number of character heights out from the edge
#     pos  is the position along the edge of the viewport, from 0 to 1.
#     just tells where the reference point of the string is: 0 = left, 1 = right, 0.5 = center.
#
# The '$pos' entry will be ignored (computed by the bargraph routine)
$pl->bargraph($labels, $values, MAXBARLABELS => 30, TEXTPOSITION => ['bv', 0.5, 1.0, 1.0]);

text

Write text on a plot. Text can either be written with respect to the borders or at an arbitrary location and angle (see the "TEXTPOSITION" entry).

Arguments:
$t : The text.

Supported options:
All options except:

BACKGROUND
DEV
FILE
FRAMECOLOR
JUST
PAGESIZE
SUBPAGES

(These must be set in call to 'new'.)

  $pl->text("Count", COLOR => 'PINK',
	    TEXTPOSITION => ['t', 3, 0.5, 0.5]); # top, 3 units out, string ref. pt in
                                                 # center of string, middle of axis

close

Close a PLplot object, writing out the file and cleaning up.

Arguments: None

Returns: Nothing

This closing of the PLplot object can be done explicitly though the 'close' method. Alternatively, a DESTROY block does an automatic close whenever the PLplot object passes out of scope.

$pl->close;

The PDL low-level interface to the PLplot library closely mimics the C API. Users are referred to the PLplot User's Manual, distributed with the source PLplot tarball. This manual is also available on-line at the PLplot web site (http://www.plplot.org/).

There are though two differences in way the functions are called. The first one is due to a limitation in the pp_def wrapper of PDL, which forces all the non-piddle arguments to be at the end of the arguments list. It is the case of strings (char *) arguments in the C API. This affects the following functions [shown below with their prototypes in PDL, with arguments preceded by "(pdl)" are piddle-convertible; see the PLplot manual for the meaning of the arguments]:

  plaxes ((pdl) x0, (pdl) y0, (pdl) xtick, (pdl) nxsub, (pdl) ytick,
          (pdl) nysub, (string) xopt, (string (yopt))
  plbox ((pdl) xtick, (pdl) nxsub, (pdl) ytick, (pdl) nysub,
         (string) xopt, (string) yopt)
  plbox3 ((pdl) xtick, (pdl) nsubx, (pdl) ytick, (pdl) nsuby,
          (pdl) ztick, (pdl) nsubz, (string) xopt, (string) xlabel,
	  (string) yopt, (string) ylabel, (string) zopt,
	  (string) zlabel)
  plmtex ((pdl) disp, (pdl) pos, (pdl) just, (string) side),
          (string) text);
  plstart ((pdl) nx, (pdl) ny, (string) devname);

The second notable different between the C and the PDL APIs is that many of the PDL calls do not need arguments to specify the size of the the vectors and/or matrices being passed. This size parameters are deduced from the size of the piddles, when possible. For now, the following interfaces are affected:

plcont (f, kx, lx, ky, ly, clevel)
plfill (x, y)
plhist (data, datmin, datmax, nbin, oldwin)
plline (x, y)
plline3 (x, y, z)
plpoly3 (x, y, z, draw, ifcc)
plmesh (x, y, z, opt)
plmeshc (x, y, z, opt, clevel)
plot3d (x, y, z, opt, side)
plpoin (x, y, code)
plpoin3 (x, y, z, code)
plscmap1l (itype, intensity, coord1, coord2, coord3, rev)
plstyl (mark, space)
plsym (x, y, code)

Some of the API functions implemented in PDL have other specificities in comparison with the C API and will be discussed below.

plxormod

$status = plxormod ($mode)

See the PLplot manual for reference.

plGetCursor

%gin = plGetCursor ()

plGetCursor waits for graphics input event and translate to world coordinates and returns a hash with the following keys:

type:      of event (CURRENTLY UNUSED)
state:     key or button mask
keysym:    key selected
button:    mouse button selected
subwindow: subwindow (alias subpage, alias subplot) number
string:    translated string
pX, pY:    absolute device coordinates of pointer
dX, dY:    relative device coordinates of pointer
wX, wY:    world coordinates of pointer

Returns an empty hash if no translation to world coordinates is possible.

plgstrm

$strm = plgstrm ()

Returns the number of the current output stream.

plgsdev

$driver = plgdev ()

Returns the current driver name.

plmkstrm

$strm = plmkstrm ()

Creates a new stream and makes it the default. Returns the number of the created stream.

plgver

$version = plgver ()