Christian Soeller > PDL-2.4.1 > PDL::Graphics::PLplot

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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;
  $pl->line($x, $y);
  $pl->close;

For more information on PLplot, see

 http://plplot.sourceforge.net

Also see the test file, test.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');

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]);
=head2 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 %150 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      
 # 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
  GREYSCALE -- from black to white via grey.
 # 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'. Special plotting symbols range from 0 to 31, 32 - 127 are ASCII characters.

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 for 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.

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--$x and $y can be continent boundary lat and lon, for example.

 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);

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(Y, X) to world coordinates via the BOX option.

 Arguments:
 $z : A 2D PDL which contains surface values at each XY coordinate.
      This PDL is stored in Y, X order, as this is how the C code of PLplot requires it.
 $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'); 
  $pl->colorkey  ($z, 'v', VIEWPORT => [0.93, 0.96, 0.15, 0.85]);

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]); 

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;

AUTHOR ^

Doug Hunt, dhunt\@ucar.edu.

SEE ALSO ^

perl(1), PDL(1), http://plplot.sourceforge.net/

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