Provided by: libpdl-graphics-gnuplot-perl_2.011-3_all bug

NAME

       PDL::Graphics::Gnuplot - Gnuplot-based plotting for PDL

SYNOPSIS

        pdl> use PDL::Graphics::Gnuplot;

        pdl> $x = sequence(101) - 50;
        pdl> gplot($x**2);
        pdl> gplot($x**2,{xr=>[0,50]});

        pdl> gplot( {title => 'Parabola with error bars'},
              with => 'xyerrorbars', legend => 'Parabola',
              $x**2 * 10, abs($x)/10, abs($x)*5 );

        pdl> $xy = zeroes(21,21)->ndcoords - pdl(10,10);
        pdl> $z = inner($xy, $xy);
        pdl> gplot({title  => 'Heat map',
                    trid   => 1,
                    view   => [0,0]
                   },
                   with => 'image', xvals($z),yvals($z),zeroes($z),$z*2
                  );

        pdl> $w = gpwin();                             # constructor
        pdl> $pi    = 3.14159;
        pdl> $theta = zeroes(200)->xlinvals(0, 6*$pi);
        pdl> $z     = zeroes(200)->xlinvals(0, 5);
        pdl> $w->plot3d(cos($theta), sin($theta), $z);
        pdl> $w->terminfo();                           # get information

DESCRIPTION

       This module allows PDL data to be plotted using Gnuplot as a backend for 2D and 3D
       plotting and image display.  Gnuplot (not affiliated with the Gnu project) is a venerable,
       open-source program that produces both interactive and publication-quality plots on many
       different output devices.  It is available through most Linux repositories, on MacOS, and
       from its website <http://www.gnuplot.info>.

       It is not necessary to understand the gnuplot syntax to generate basic, or even complex,
       plots - though the full syntax is available for advanced users who want the full
       flexibility of the Gnuplot backend.

       Gnuplot recognizes both hard-copy and interactive plotting devices, and on interactive
       devices (like X11) it is possible to pan, scale, and rotate both 2-D and 3-D plots
       interactively.  You can also enter graphical data through mouse clicks on the device
       window.  On some hardcopy devices (e.g. "PDF") that support multipage output, it is
       necessary to close the device after plotting to ensure a valid file is written out.

       "PDL::Graphics::Gnuplot" exports two routines by default: a constructor, "gpwin()" and a
       general purpose plot routine, "gplot()".  Depending on options, "gplot()" can produce line
       plots, scatterplots, error boxes, "candlesticks", images, or any overlain combination of
       these elements; or perspective views of 3-D renderings such as surface plots.

       A call to "gplot()" looks like:

        gplot({temp_plot_options}, # optional hash ref
             curve_options, data, data, ... ,
             curve_options, data, data, ... );

       The data entries are columns to be plotted.  They are normally an optional ordinate and a
       required abscissa, but some plot modes can use more columns than that.  The collection of
       columns is called a "tuple".  Each column must be a separate PDL or an ARRAY ref.  If all
       the columns are PDLs, you can add extra dimensions to make threaded collections of curves.

       PDL::Graphics::Gnuplot also implements an object oriented interface. Plot objects track
       individual gnuplot subprocesses.  Direct calls to "gplot()" are tracked through a global
       object that stores globally set configuration variables.

       The "gplot()" sub (or the "plot()" method) collects two kinds of options hash: plot
       options, which describe the overall structure of the plot being produced (e.g. axis
       specifications, window size, and title), and curve options, which describe the behavior of
       individual traces or collections of points being plotted.  In addition, the module itself
       supports options that allow direct pass-through of plotting commands to the underlying
       gnuplot process.

   Basic plotting
       Gnuplot generates many kinds of plot, from basic line plots and histograms to scaled
       labels.  Individual plots can be 2-D or 3-D, and different sets of plot styles are
       supported in each mode.  Plots can be sent to a variety of devices; see the description of
       plot options, below.

       You can specify what type of graphics output you want, but in most cases doing nothing
       will cause a plot to be rendered on your screen: with X windows on UNIX or Linux systems,
       with an XQuartz windows on MacOS, or with a native window on Microsoft Windows.

       You select a plot style with the "with" curve option, and feed in columns of data (usually
       ordinate followed by abscissa).  The collection of columns is called a "tuple".  These
       plots have two columns in their tuples:

        $x = xvals(51)-25; $y = $x**2;
        gplot(with=>'points', $x, $y);  # Draw points on a parabola
        gplot(with=>'lines', $x, $y);   # Draw a parabola
        gplot({title=>"Parabolic fit"},
              with=>"yerrorbars", legend=>"data", $x, $y+(random($y)-0.5)*2*$y/20, pdl($y/20),
              with=>"lines",      legend=>"fit",  $x, $y);

       Normal threading rules apply across the arguments to a given plot.

       All data are required to be supplied as either PDLs or list refs.  If you use a list ref
       as a data column, then normal threading is disabled.  For example:

        $x = xvals(5);
        $y = xvals(5)**2;
        $labels = ['one','two','three','four','five'];
        gplot(with=>'labels',$x,$y,$labels);

       See below for supported curve styles.

       Modifying plots

       Gnuplot is built around a monolithic plot model - it is not possible to add new data
       directly to a plot without redrawing the entire plot. To support replotting,
       PDL::Graphics::Gnuplot stores the data you plot in the plot object, so that you can add
       new data with the "replot" command:

        $w=gpwin(x11);
        $x=xvals(101)/100;
        $y=$x;
        $w->plot($x,$y);
        $w->replot($x,$y*$y);

       For speed, the data are *not* disconnected from their original variables - so this will
       plot X vs. sqrt(X):

        $x = xvals(101)/100;
        $y = xvals(101)/100;
        $w->plot($x,$y);
        $y->inplace->sqrt;
        $w->replot();

       Plotting to an image file or device

       PDL:Graphics::Gnuplot can plot to most of the devices supported by gnuplot itself.  You
       can specify the file type with the "output" method or the object constructor "gplot".
       Either one will allow you to name a type of file to produce, and a collection of options
       speciic to that type of output file.

       Image plotting

       Several of the plot styles accept image data.  The tuple parameters work the same way as
       for basic plots, but each "column" is a 2-D PDL rather than a 1-D PDL.  As a special case,
       the "with image" plot style accepts either a 2-D or a 3-D PDL.  If you pass in 3-D PDL,
       the extra dimension can have size 1, 3, or 4.  It is interpreted as running across
       (R,G,B,A) color planes.

       3-D plotting

       You can plot in 3-D by setting the plot option "trid" to a true value.  Three dimensional
       plots accept either 1-D or 2-D PDLs as data columns.  If you feed in 2-D "columns", many
       of the common plot styles will generalize appropriately to 3-D.  For example, to plot a
       2-D surface as a line grid, you can use the "lines" style and feed in 2-D columns instead
       of 1-D columns.

   Enhanced text
       Most gnuplot output devices include the option to markup "enhanced text". That means text
       is interpreted so that you can change its font and size, and insert superscripts and
       subscripts into labels.  Codes are:

       {} Text grouping - enclose text in braces to group characters, as in LaTeX.

       ^  Superscript the next character or group (shrinks it slightly too where that is
          supported).

       _  Subscript the next character or group (shrinks it slightly too where that is
          supported).

       @  Phantom box (occupies no width; controls height for super- and subscripting)

       &  Controllable-width space, e.g. &amp;{template-string}

       ~  overstrike -- e.g. ~a{0.8-} overprints '-' on 'a', raised by 0.8xfontsize.

       {/[fontname][=fontsize | *fontscale] text}
          Change font to (optional) fontname, and optional absolute font size or relative font
          scale ("fontsize" and "fontscale" are numbers).  The space after the size parameter is
          not rendered.

       \  Backslash escapes control characters to render them as themselves.

   Color specification
       There are several contexts where you can specify color of plot elements.  In those places,
       you can specify colors exactly as in the Gnuplot manual, or more tersely.  In general, a
       color spec can be any one of the following:

       - an integer
          This specifies a recognizable unique color in the same order as used by the plotting
          engine.

       - the name of a color
          (e.g. "blue").  Supported color names are listed in the variable
          @Alien::Gnuplot::colors.

       - an RGB value string
          Strings have the form "#RRGGBB", where the "#" is literal and the RR, GG, and BB are
          hexadecimal bytes.

       - the word "palette"
          "palette" indicates that color is to be drawn from the scaled colorbar palette (which
          you can set with the "clut" plot option), by lookup using an additional column in the
          associated data tuple.

       - the word "variable"
          "variable" indicates that color is to be drawn from the integer plotting colors used by
          the plotting engine, indexed by an additional column in the associated data tuple.

       - the phrase "rgb variable"
          "rgb variable" indicates that color is to be directly specified by a 24 bit integer
          specifying 8-bit values for (from most significant byte to least significant byte) R,
          G, and B in the output color.  The integer is drawn from an additional column in the
          associated data tuple.

   Plot styles supported
       Gnuplot itself supports a wide range of plot styles, and all are supported by
       PDL::Graphics::Gnuplot.  Most of the basic plot styles collect tuples of 1-D columns in
       2-D mode (for ordinary plots), or either 1-D or 2-D "columns" in 3-D mode (for grid
       surface plots and such).  Image modes always collect tuples made of 2-D "columns".

       You can pass in 1-D columns as either PDLs or ARRAY refs.  That is important for plot
       types (such as "labels") that require a collection of strings rather than numeric data.

       Each plot style can by modified to support particular colors or line style options.  These
       modifications get passed in as curve options (see below). For example, to plot a blue line
       you can use "with=>'lines',lc=>'blue'".  To match the autogenerated style of a particular
       line you can use the "ls" curve option.

       The GNuplot plot styles supported are:

       ·  "boxerrorbars" - combo of "boxes" and "yerrorbars", below (2D)

       ·  "boxes" - simple boxes around regions on the plot (2D)

       ·  "boxxyerrorbars" - Render X and Y error bars as boxes (2D)

       ·  "candlesticks" - Y error bars with inner and outer limits (2D)

       ·  "circles" - circles with variable radius at each point: X/Y/radius (2D)

       ·  "dots" - tiny points ("dots") at each point, e.g. for scatterplots (2D/3D)

       ·  "ellipses" - ellipses.  Accepts X/Y/major/minor/angle (2D)

       ·  "filledcurves" - closed polygons or axis-to-line filled shapes (2D)

       ·  "financebars" - financial style plot. Accepts date/open/low/high/close (2D)

       ·  "fsteps" - square bin plot; delta-Y, then delta-X (see "steps", "histeps") (2D)

       ·  "histeps" - square bin plot; plateaus centered on X coords (see "fsteps", "steps") (2D)

       ·  "histogram" - binned histogram of dataset (not direct plot; see "newhistogram") (2D)

       ·  "fits" - (PDL-specific) renders FITS image files in scientific coordinates

       ·  "image" - Takes (i), (x,y,i), or (x,y,z,i).  See "rgbimage", "rgbalpha", "fits".
          (2D/3D)

       ·  "impulses" - vertical line from axis to the plotted point (2D/3D)

       ·  "labels" - Text labels at specified locations all over the plot (2D/3D)

       ·  "lines" - regular line plot (2D/3D)

       ·  "linespoints" - line plot with symbols at plotted points (2D/3D)

       ·  "newhistogram" - multiple-histogram-friendly histogram style (see "histogram") (2D)

       ·  "points" - symbols at plotted points (2D/3D)

       ·  "rgbalpha" - R/G/B color image with variable transparency (2D/3D)

       ·  "rgbimage" - R/G/B color image (2D/3D)

       ·  "steps" - square bin plot; delta-X, then delta-Y (see "fsteps", "histeps") (2D)

       ·  "vectors" - Small arrows: (x,y,[z]) -> (x+dx,y+dy,[z+dz]) (2D/3D)

       ·  "xerrorbars" - points with X error bars ("T" form) (2D)

       ·  "xyerrorbars" - points with both X and Y error bars ("T" form) (2D)

       ·  "yerrorbars" - points with Y error bars ("T" form) (2D)

       ·  "xerrorlines" - line plot with X errorbars at each point.  (2D)

       ·  "xyerrorlines" - line plot with XY errorbars at each point. (2D)

       ·  "yerrorlines" - line plot with Y error limits at each point. (2D)

       ·  "pm3d" - three-dimensional variable-position surface plot

   Options arguments
       The plot options are parameters that affect the whole plot, like the title of the plot,
       the axis labels, the extents, 2d/3d selection, etc. All the plot options are described
       below in "Plot Options".  Plot options can be set in the plot object, or passed to the
       plotting methods directly.  Plot options can be passed in as a leading interpolated hash,
       as a leading hash ref, or as a trailing hash ref in the argument list to any of the main
       plotting routines ("gplot", "plot", "image", etc.).

       The curve options are parameters that affect only one curve in particular. Each call to
       "plot()" can contain many curves, and options for a particular curve precede the data for
       that curve in the argument list. The actual type of curve (the "with" option) is
       persistent, but all other curve options and modifiers are not.  An example:

        gplot( with => 'points',  $x, $a,
               {axes=> x1y2},     $x, $b,
               with => 'lines',   $x, $c );

       This plots 3 curves: $a vs. $x plotted with points on the main y-axis (this is the
       default), $b vs. $x plotted with points on the secondary y axis, and $c vs. $x plotted
       with lines on the main y-axis (the default). Note that the curve options can be supplied
       as either an inline hash or a hash ref.

       All the curve options are described below in "Curve Options".

       If you want to plot multiple curves of the same type without setting any curve options
       explicitly, you must include an empty hash ref between the tuples for subsequent lines, as
       in:

        gplot( $x, $a, {}, $x, $b, {}, $x, $c );

   Data arguments
       Following the curve options in the "plot()" argument list is the actual data being
       plotted. Each output data point is a "tuple" whose size varies depending on what is being
       plotted. For example if we're making a simple 2D x-y plot, each tuple has 2 values; if
       we're making a 3d plot with each point having variable size and color, each tuple has 5
       values (x,y,z,size,color). Each tuple element must be passed separately.  For ordinary 2-D
       plots, the 0 dim of the tuple elements runs across plotted point.  PDL threading is
       active, so you can plot multiple curves with similar curve options on a normal 2-D plot,
       just by stacking data inside the passed-in PDLs.  (An exception is that threading is
       disabled if one or more of the data elements is a list ref).

       PDLs vs list refs

       The usual way to pass in data is as a PDL -- one PDL per column of data in the tuple.  But
       strings, in particular, cannot easily be hammered into PDLs.  Therefore any column in each
       tuple can be a list ref containing values (either numeric or string).  The column is
       interpreted using the usual polymorphous cast-behind-your-back behavior of Perl.  For the
       sake of sanity, if even one list ref is present in a tuple, then threading is disabled in
       that tuple: everything has to have a nice 1-D shape.

       Implicit domains

       When making a simple 2D plot, if exactly 1 dimension is missing, PDL::Graphics::Gnuplot
       will use sequence(N) as the domain. This is why code like "plot(pdl(1,5,3,4,4) )" works.
       Only one PDL is given here, but the plot type ("lines" by default) requires 2 elements per
       tuple. We are thus exactly 1 piddle short; sequence(5) is used as the missing domain PDL.
       This is thus equivalent to "plot(sequence(5), pdl(1,5,3,4,4) )".

       If plotting in 3d or displaying an image, an implicit domain will be used if we are
       exactly 2 piddles short. In this case, PDL::Graphics::Gnuplot will use a 2D grid as a
       domain. Example:

        my $xy = zeros(21,21)->ndcoords - pdl(10,10);
        gplot({'3d' => 1},
               with => 'points', inner($xy, $xy));
        gplot( with => 'image',  sin(rvals(51,51)) );

       Here the only given piddle has dimensions (21,21). This is a 3D plot, so we are exactly 2
       piddles short. Thus, PDL::Graphics::Gnuplot generates an implicit domain, corresponding to
       a 21-by-21 grid.

       "PDL::Graphics::Gnuplot" requires explicit separators between tuples for different plots,
       so it is always clear from the arguments you pass in just how many columns you are
       supplying. For example, "plot($a,$b)" will plot $b vs. $a.  If you actually want to plot
       an overlay of both $a and $b against array index, you want "plot($a,{},$b)" instead.  The
       "{}" is a hash ref containing a collection of all the curve options that you are changing
       between the two curves -- in this case, zero of them.

   Images
       PDL::Graphics::Gnuplot supports four styles of image plot, via the "with" curve option.

       The "image" style accepts a single image plane and displays it using the palette
       (pseudocolor map) that is specified in the plot options for that plot.  As a special case,
       if you supply as data a (3xWxH) or (WxHx3) PDL it is treated as an RGB image and displayed
       with the "rgbimage" style (below), provided there are at least 5 pixels in each of the
       other two dimensions (just to be sure).  For quick image display there is also an "image"
       method:

        use PDL::Graphics::Gnuplot qw/image gplot/;
        $im = sin(rvals(51,51)/2);
        image( $im );                # display the image
        gplot( with=>'image', $im );  # display the image (longer form)

       The colors are autoscaled in both cases.  To set a particular color range, use the
       'cbrange' plot option:

        image( {cbrange=>[0,1]}, $im );

       You can plot rgb images directly with the image style, just by including a 3rd dimension
       of size 3 on your image:

        $rgbim = pdl( xvals($im), yvals($im),rvals($im)/sqrt(2));
        image( $rgbim );                # display an RGB image
        gplot( with=>'image', $rgbim ); # display an RGB image (longer form)

       Some additional plot styles exist to specify RGB and RGB transparent forms directly.
       These are the "with" styles "rgbimage" and "rgbalpha".  For each of them you must specify
       the channels as separate PDLs:

        gplot( with=>'rgbimage', $rgbim->dog );               # RGB  the long way
        gplot( with=>'rgbalpha', $rgbim->dog, 255*($im>0) );  # RGBA the long way

       According to the gnuplot specification you can also give X and Y values for each pixel, as
       in

        gplot( with=>'image', xvals($im), yvals($im), $im )

       but this appears not to work properly for anything more complicated than a trivial matrix
       of X and Y values.

       PDL::Graphics::Gnuplot provides a "fits" plot style that interprets World Coordinate
       System (WCS) information supplied in the header of the scientific image format FITS. The
       image is displayed in rectified scientific coordinates, rather than in pixel coordinates.
       You can plot FITS images in scientific coordinates with

        gplot( with=>'fits', $fitsdata );

       The fits plot style accepts a modifier "resample" (which may be abbreviated), that allows
       you to downsample and/or rectify the image before it is passed to the Gnuplot back-end.
       This is useful either to cut down on the burden of transferring large blocks of image data
       or to rectify images with nonlinear WCS transformations in their headers.  (gnuplot itself
       has a bug that prevents direct rendering of images in nonlinear coordinates).

        gplot( with=>'fits res 200', $fitsdata );
        gplot( with=>'fits res 100,400',$fitsdata );

       to specify that the output are to be resampled onto a square 200x200 grid or a 100x400
       grid, respectively.  The resample sizes must be positive integers.

   Interactivity
       Several of the graphical backends of Gnuplot are interactive, allowing you to pan, zoom,
       rotate and measure the data interactively in the plot window. See the Gnuplot
       documentation for details about how to do this. Some terminals (such as "wxt") are
       persistently interactive. Other terminals (such as "x11") maintain their interactivity
       only while the underlying gnuplot process is active -- i.e. until another plot is created
       with the same PDL::Graphics::Gnuplot object, or until the perl process exits (whichever
       comes first).  Still others (the hardcopy devices) aren't interactive at all.

       Some interactive devices (notably "wxt" and "x11") also support mouse input: you can write
       PDL scripts that accept and manipulate graphical input from the plotted window.

PLOT OPTIONS

       Gnuplot controls plot style with "plot options" that configure and specify virtually all
       aspects of the plot to be produced.   Plot options are tracked as stored state in the
       PDL::Graphics::Gnuplot object.  You can set them by passing them in to the constructor, to
       an "options" method, or to the "plot" method itself.

       Nearly all the underlying Gnuplot plot options are supported, as well as some additional
       options that are parsed by the module itself for convenience.

       There are many, many plot options.  For convenience, we've grouped them by general
       category below.  Each group has a heading "POs for <foo>", describing the category.  You
       can skip below them all if you want to read about curve options or other aspects of
       PDL::Graphics::Gnuplot.

   POs for Output: terminal, termoption, output, device, hardcopy
       You can send plots to a variety of different devices; Gnuplot calls devices "terminals".
       With the object-oriented interface, you must set the output device with the constructor
       "PDL::Graphics::Gnuplot::new" (or the exported constructor "gpwin") or the "output"
       method.  If you use the simple non-object interface, you can set the output with the
       "terminal", "termoption", and "output" plot options.

       "terminal" sets the output device type for Gnuplot, and "output" sets the actual output
       file or window number.

       "device" and "hardcopy" are for convenience. "device" offers a PGPLOT-style device
       specifier in "filename/device" format (the "filename" gets sent to the "output" option,
       the "device" gets sent to the "terminal" option). "hardcopy" takes an output file name,
       attempts to parse out a file suffix and infer a device type. "hardcopy" also uses a common
       set of terminal options needed to fill an entire letter page with a plot.

       For finer grained control of the plotting environment, you can send "terminal options" to
       Gnuplot.  If you set the terminal directly with plot options, you can include terminal
       options by interpolating them into a string, as in "terminal jpeg interlace butt crop", or
       you can use the constructor "new" (also exported as "gpwin"), which parses terminal
       options as an argument list.

       The routine "PDL::Graphics::Gnuplot::terminfo" prints a list of all available terminals
       or, if you pass in a terminal name, options accepted by that terminal.

   POs for Titles
       The options described here are

       title
       xlabel
       x2label
       ylabel
       y2label
       zlabel
       cblabel
       key

       Gnuplot supports "enhanced" text escapes on most terminals; see "text", below.

       The "title" option lets you set a title for the whole plot.

       Individual plot components are labeled with the "label" options.  "xlabel", "x2label",
       "ylabel", and "y2label" specify axis titles for 2-D plots.  The "zlabel" works for 3-D
       plots.  The "cblabel" option sets the label for the color box, in plot types that have one
       (e.g.  image display).

       (Don't be confused by "clabel", which doesn't set a label at all, rather specifies the
       printf format used by contour labels in contour plots.)

       "key" controls where the plot key (that relates line/symbol style to label) is placed on
       the plot.  It takes a scalar boolean indicating whether to turn the key on (with default
       values) or off, or a list ref containing any of the following arguments (all are optional)
       in the order listed:

       ·  ( on | off ) - turn the key on or off

       ·  ( inside | outside | lmargin | rmargin | tmargin | bmargin | at <pos> )

          These keywords set the location of the key -- "inside/outside" is relative to the plot
          border; the margin keywords indicate location in the margins of the plot; and at <pos>
          (where <pos> is a comma-delimited string containing (x,y): "key=>[at=>"0.5,0.5"]") is
          an exact location to place the key.

       ·  ( left | right | center ) ( top | bottom | center ) - horiz./vert. alignment

       ·  ( vertical | horizontal ) - stacking direction within the key

       ·  ( Left | Right ) - justification of plot labels within the key (note case)

       ·  [no]reverse - switch order of label and sample line

       ·  [no]invert - invert the stack order of the labels

       ·  samplen <length> - set the length of the sample lines

       ·  spacing <dist> - set the spacing between adjacent labels in the list

       ·  [no]autotitle - control whether labels are generated when not specified

       ·  title "<text>" - set a title for the key

       ·  [no]enhanced - override terminal settings for enhanced text interpretation

       ·  font "<face>,<size>" - set font for the labels

       ·  textcolor <colorspec>

       ·  [no]box linestyle <ls> linetype <lt> linewidth <lw> - control box around the key

   POs for axes, grids, & borders
       The options described here are

       grid
       xzeroaxis
       x2zeroaxis
       yzeroaxis
       y2zeroaxis
       zzeroaxis
       border

       Normally, tick marks and their labels are applied to the border of a plot, and no extra
       axes (e.g. the y=0 line) nor coordinate grids are shown.  You can specify which (if any)
       zero axes should be drawn, and which (if any) borders should be drawn.

       The "border" option controls whether the plot itself has a border drawn around it.  You
       can feed it a scalar boolean value to indicate whether borders should be drawn around the
       plot -- or you can feed in a list ref containing options.  The options are all optional
       but must be supplied in the order given.

       ·  <integer> - packed bit flags for which border lines to draw

          The default if you set a true value for "border" is to draw all border lines.  You can
          feed in a single integer value containing a bit mask, to draw only some border lines.
          From LSB to MSB, the coded lines are bottom, left, top, right for 2D plots -- e.g. 5
          will draw bottom and top borders but neither left nor right.

          In three dimensions, 12 bits are used to describe the twelve edges of a cube
          surrounding the plot.  In groups of three, the first four control the bottom (xy) plane
          edges in the same order as in the 2-D plots; the middle four control the vertical edges
          that rise from the clockwise end of the bottom plane edges; and the last four control
          the top plane edges.

       ·  ( back | front ) - draw borders first or last (controls hidden line appearance)

       ·  linewidth <lw>, linestyle <ls>, linetype <lt>

          These are Gnuplot's usual three options for line control.

       The "grid" option indicates whether gridlines should be drawn on each axis.  It takes a
       list ref of arguments, each of which is either "no" or "m" or "", followed by an axis name
       and "tics" -- e.g. "grid=>["noxtics","ymtics"]" draws no X gridlines and draws
       (horizontal) Y gridlines on Y axis major and minor tics, while "grid=>["xtics","ytics"]"
       or "grid=>["xtics ytics"]" will draw both vertical (X) and horizontal (Y) grid lines on
       major tics.

       To draw a coordinate grid with default values, set "grid=>1".  For more control, feed in a
       list ref with zero or more of the following parameters, in order:

       The "zeroaxis" keyword indicates whether to actually draw each axis line at the
       corresponding zero along its indicated dimension.  For example, to draw the X axis (y=0),
       use "xzeroaxis=>1".  If you just want the axis turned on with default values, you can feed
       in a Boolean scalar; if you want to set its parameters, you can feed in a list ref
       containing linewidth, linestyle, and linetype (with appropriate parameters for each), e.g.
       "xzeroaxis=>[linewidth=>2]".

   POs for axis range and mode
       The options described here are

       xrange
       x2range
       yrange
       y2range
       zrange
       rrange
       cbrange
       trange
       urange
       vrange
       autoscale
       logscale

       Gnuplot accepts explicit ranges as plot options for all axes.  Each option accepts a list
       ref with (min, max).  If either min or max is missing, then the opposite limit is
       autoscaled.  The x and y ranges refer to the usual ordinate and abscissa of the plot; x2
       and y2 refer to alternate ordinate and abscissa; z if for 3-D plots; r is for polar plots;
       t, u, and v are for parametric plots.  cb is for the color box on plots that include it
       (see "color", below).

       "rrange" is used for radial coordinates (which are accessible using the "mapping" plot
       option, below).

       "cbrange" (for 'color box range') sets the range of values over which palette colors
       (either gray or pseudocolor) are matched.  It is valid in any color-mapped plot (including
       images or palette-mapped lines or points), even if no color box is being displayed for
       this plot.

       "trange", "urange", and "vrange" set ranges for the parametric coordinates if you are
       plotting a parametric curve.

       By default all axes are autoscaled unless you specify a range on that axis, and partially
       (min or max) autoscaled if you specify a partial range on that axis.  "autoscale" allows
       more explicit control of how autoscaling is performed, on an axis-by-axis basis.  It
       accepts a hash ref, each element of which specifies how a single axis should be
       autoscaled.  Each keyword contains an axis name followed by one of "fix", "min", "max",
       "fixmin", or "fixmax".  You can set all the axes at once by setting the keyword name to '
       '.  Examples:

        autoscale=>{x=>'max',y=>'fix'};

       There is an older list ref syntax which is deprecated but still accepted.

       To not autoscale an axis at all, specify a range for it. The fix style of autoscaling
       forces the autoscaler to use the actual min/max of the data as the limit for the
       corresponding axis -- by default the axis gets extended to the next minor tic (as set by
       the autoticker or by a tic specification, see below).

       "logscale" allows you to turn on logarithmic scaling for any or all axes, and to set the
       base of the logarithm.  It takes a list ref, the first element of which is a string
       mushing together the names of all the axes to scale logarithmically, and the second of
       which is the base of the logarithm: "logscale=>[xy=>10]".  You can also leave off the base
       if you want base-10 logs: "logscale=>['xy']".

   POs for Axis tick marks
       The options described here are

       xtics
       x2tics
       ytics
       y2tics
       ztics
       cbtics
       mxtics
       mx2tics
       mytics
       my2tics
       mztics
       mcbtics

       Axis tick marks are called "tics" within Gnuplot, and they are extensively controllable
       via the "{axis}tics" options.  In particular, major and minor ticks are supported, as are
       arbitrarily variable length ticks, non-equally spaced ticks, and arbitrarily labelled
       ticks.  Support exists for time formatted ticks (see "POs for time data values" below).

       By default, gnuplot will automatically place major and minor ticks.  You can turn off
       ticks on an axis by setting the appropriate {foo}tics option to a defined, false scalar
       value (e.g. "xtics=>0").  If you want to set major tics to happen at a regular specified
       intervals, you can set the appropriate tics option to a nonzero scalar value (e.g.
       "xtics=>2" to specify a tic every 2 units on the X axis).  To use default values for the
       tick positioning, specify an empty hash or array ref (e.g. "xtics=>{}"), or a string
       containing only whitespace (e.g. "xtics=>' '").

       If you prepend an 'm' to any tics option, it affects minor tics instead of major tics
       (major tics typically show units; minor tics typically show fractions of a unit).

       Each tics option can accept a hash ref containing options to pass to Gnuplot.  You can
       also pass in a snippet of gnuplot command, as either a string or an array ref -- but those
       techniques are deprecated and may disappear in a future version of
       "PDL:Graphics::Gnuplot".

       The keywords are case-insensitive and may be abbreviated, just as with other option types.
       They are:

       · axis - set to 1 to place tics on the axis (the default)

       · border - set to 1 to place tics on the border (not the default)

       · mirror - set to 1 to place mirrored tics on the opposite axis/border (the default,
         unless an alternate axis interferes -- e.g. y2)

       · in - set to 1 to draw tics inward from the axis/border

       · out - set to 1 to draw tics outward from the axis/border

       · scale - multiplier on tic length compared to the default

         If you pass in undef, tics get the default length.  If you pass in a scalar, major tics
         get scaled.  You can pass in an array ref to scale minor tics too.

       · rotate - turn label text by the given angle (in degrees) on the drawing plane

       · offset - offset label text from default position, (units: characters; requires array ref
         containing x,y)

       · locations - sets tic locations.  Gets an array ref: [incr], [start, incr], or [start,
         incr, stop].

       · labels - sets tic locations explicitly, with text labels for each. If you specify both
         "locations" and "labels", you get both sets of tics on the same axis.

         The labels should be a nested list ref that is a collection of duals or triplets.  Each
         dual or triplet should contain [label, position, minorflag], as in
         "labels=>[["one",1,0],["three-halves",1.5,1],["two",2,0]]".

       · format - printf-style format string for tic labels.  There are some extensions to the
         gnuplot format tags -- see the gnuplot manual.  Gnuplot 4.8 and higher have %h, which
         works like %g but uses extended text formatting if it is available.

       · font - set font name and size (system font name)

       · rangelimited - set to 1 to limit tics to the range of values actually present in the
         plot

       · textcolor - set the color of the ticks (see "color specs" below)

       For example, to turn on inward mirrored X axis ticks with diagonal Arial 9 text, use:

        xtics => {axis=>1,mirror=>1,in=>1,rotate=>45,font=>'Arial,9'}

       or

        xtics => ['axis','mirror','in','rotate by 45','font "Arial,9"']

   POs for time data values
       The options described here are

       xmtics
       x2mtics
       ymtics
       y2mtics
       zmtics
       cbmtics
       xdtics
       x2dtics
       ydtics
       y2dtics
       zdtics
       cbdtics
       xdata
       x2data
       ydata
       y2data
       zdata
       cbdata

       Gnuplot contains support for plotting absolute time and date on any of its axes, with
       conventional formatting. There are three main methods, which are mutually exclusive (i.e.
       you should not attempt to use two at once on the same axis).

       Plotting timestamps using UNIX times
          You can set any axis to plot timestamps rather than numeric values by setting the
          corresponding "data" plot option to "time", e.g. "xdata=>"time"".  If you do so, then
          numeric values in the corresponding data are interpreted as UNIX time (seconds since
          the UNIX epoch, neglecting leap seconds).  No provision is made for UT"-"TAI
          conversion.  You can format how the times are plotted with the "format" option in the
          various "tics" options(above).  Output specifiers should be in UNIX strftime(3) format
          -- for example, "xdata=>"time",xtics=>{format=>"%Y-%b-%dT%H:%M:%S"}" will plot UNIX
          times as ISO timestamps in the ordinate.

          Due to limitations within gnuplot, the time resolution in this mode is limited to 1
          second - if you want fractional seconds, you must use numerically formatted times
          (and/or create your own tick labels using the "labels" suboption to the "?tics" option.

          Timestamp format specifiers

          Time format specifiers use the following printf-like codes:

          ·  Year A.D.: %Y is 4-digit year; %y is 2-digit year (1969-2068)

          ·  Month of year: %m: 01-12; %b or %h: abrev. name; %B: full name

          ·  Week of year: %W (week starting Monday); %U (week starting Sunday)

          ·  Day of year: %j (1-366; boundary is midnight)

          ·  Day of month: %d (01-31)

          ·  Day of week: %w (0-6, Sunday=0), %a (abrev. name), %A (full name)

          ·  Hour of day: %k (0-23); %H (00-23); %l (1-12); %I (01-12)

          ·  Am/pm: %p ("am" or "pm")

          ·  Minute of hour: %M (00-60)

          ·  Second of minute: %S (0-60)

          ·  Total seconds since start of 2000 A.D.: %s

          ·  Timestamps: %T (same as "%H:%M:%S"); %R (same as "%H:%M"); %r (same as "%I:%M:%S
             %p")

          ·  Datestamps: %D (same as "%m/%d/%y"); %F (same as "%Y-%m-%d")

          ·  ISO timestamps: use "%DT%T".

       day-of-week plotting
          If you just want to plot named days of the week, you can instead use the "dtics"
          options set plotting to day of week, where 0 is Sunday and 6 is Saturday; values are
          interpreted modulo 7.  For example, "xmtics=>1,xrange=>[-4,9]" will plot two weeks from
          Wednesday to Wednesday. As far as output format goes, this is exactly equivalent to
          using the %w option with full formatting - but you can treat the numeric range in terms
          of weeks rather than seconds.

       month-of-year plotting
          The "mtics" options set plotting to months of the year, where 1 is January and 12 is
          December, so "xdtics=>1, xrange=>[0,4]" will include Christmas through Easter.  This is
          exactly equivalent to using the %d option with full formatting - but you can treat the
          numeric range in terms of months rather than seconds.

   POs for location/size
       The options described here are

       tmargin
       bmargin
       lmargin
       rmargin
       offsets
       origin
       size
       justify
       clip

       Adjusting the size, location, and margins of the plot on the plotting surface is something
       of a null operation for most single plots -- but you can tweak the placement and size of
       the plot with these options.  That is particularly useful for multiplots, where you might
       like to make an inset plot or to lay out a set of plots in a custom way.

       The margin options accept scalar values -- either a positive number of character heights
       or widths of margin around the plot compared to the edge of the device window, or a string
       that starts with "at screen " and interpolates a number containing the fraction of the
       plot window offset.  The "at screen" technique allows exact plot placement and is an
       alternative to the "origin" and "size" options below.

       The "offsets" option allows you to put an empty boundary around the data, inside the plot
       borders, in an autosacaled graph.  The offsets only affect the x1 and y1 axes, and only in
       2D plot commands.  "offsets" accepts a list ref with four values for the offsets, which
       are given in scientific (plotted) axis units.

       The "origin" option lets you specify the origin (lower left corner) of an individual plot
       on the plotting window.  The coordinates are screen coordinates -- i.e. fraction of the
       total plotting window.

       The size option lets you adjust the size and aspect ratio of the plot, as an absolute
       fraction of the plot window size.  You feed in fractional ratios, as in "size=>[$xfrac,
       $yfrac]".  You can also feed in some keywords to adjust the aspect ratio of the plot.  The
       size option overrides any autoscaling that is done by the auto-layout in multiplot mode,
       so use with caution -- particularly if you are multiplotting.  You can use "size" to
       adjust the aspect ratio of a plot, but this is deprecated in favor of the pseudo-option
       "justify".

       "justify" sets the scientific aspect ratio of a 2-D plot.  Unity yields a plot with a
       square scientific aspect ratio.  Larger numbers yield taller plots.

       "clip" controls the border between the plotted data and the border of the plot.  There are
       three clip types supported:   points, one, and two.  You can set them independently by
       passing in booleans with their names: "clip=>[points=>1,two=>0]".

   POs for Color: colorbox, palette, clut, pseudocolor, pc, perceptual, pcp
       Color plots are supported via RGB and pseudocolor.  Plots that use pseudcolor or grayscale
       can have a "color box" that shows the photometric meaning of the color.

       The colorbox generally appears when necessary but can be controlled manually with the
       "colorbox" option.  "colorbox" accepts a scalar boolean value indicating whether or no to
       draw a color box, or a list ref containing additional options.  The options are all, well,
       optional but must appear in the order given:

       ( vertical | horizontal ) - indicates direction of the gradient in the box
       ( default | user ) - indicates user origin and size
          If you specify "default" the colorbox will be placed on the right-hand side of the
          plot; if you specify "user", you give the location and size in subsequent arguments:

           colorbox => [ 'user', 'origin'=>"$x,$y", 'size' => "$x,$y" ]

       ( front | back ) - draws the colorbox before or after the plot
       ( noborder | bdefault | border <line style> ) - specify border
          The line style is a numeric type as described in the gnuplot manual.

       The "palette" option offers many arguments that are not fully documented in this version
       but are explained in the gnuplot manual.  It offers complete control over the pseudocolor
       mapping function.

       For simple color maps, "clut" gives access to a set of named color maps.  (from "Color
       Look Up Table").  A few existing color maps are: "default", "gray", "sepia", "ocean",
       "rainbow", "heat1", "heat2", and "wheel".  To see a complete list, specify an invalid
       table, e.g. "clut=>'xxx'".  "clut" is maintained but is superseded by "pc" and "pcp"
       (below), which give access to a better variety of color tables, and have better support
       for scientific images.

       "pseudocolor" (synonym "pc") gives access to the color tables built in to the
       "PDL::Transform::Color" package, if that package is available.  It takes either a color
       table name or a list ref which is a collection of arguments that get sent to the
       "PDL::Transform::Color::t_pc" transform definition method. Sending the empty string or
       undef will generate a list of allowable color table names.  Many of the color tables are
       "photometric" and will render photometric data correctly without gamma correction.

       "perceptual" (synonym "pcp") gives the same access to "PDL::Transform::Color" as does
       "pseudocolor", but the "equal-perceptual-difference" scaling is used -- i.e. input values
       are gamma-corrected by the module so that uniform shifts in numeric value yield
       approximately uniform perceptual shifts.

       If you use "pseudocolor" or "perceptual", and if "PDL::Transform::Color" can be loaded,
       then the external module is used to define a custom Gnuplot palette by linear
       interpolation across 256 values.  That palette is then used to translate your monochrome
       data to a color image.  The Gnuplot output is assumed to be sRGB.  This is probably OK for
       most output devices.

   POs for 3D: trid, view, pm3d, hidden3d, dgrid3d, surface, xyplane, mapping
       If "trid" or its synonym "3d" is true, Gnuplot renders a 3-D plot.  This changes the
       default tuple size from 2 to 3.  This option is used to switch between the Gnuplot "plot"
       and "splot" command, but it is tracked with persistent state just as any other option.

       The "view" option controls the viewpoint of the 3-D plot.  It takes a list of numbers:
       "view=>[$rot_x, $rot_z, $scale, $scale_z]".  After each number, you can omit the
       subsequent ones.  Alternatively, "view=>['map']" represents the drawing as a map (e.g. for
       contour plots) and "view=>[equal=>'xy']" forces equal length scales on the X and Y axes
       regardless of perspective, while "view=>[equal=>'xyz']" sets equal length scales on all
       three axes.

       The "pm3d" option accepts several parameters to control the pm3d plot style, which is a
       palette-mapped 3d surface.  They are not documented here in this version of the module but
       are explained in the gnuplot manual.

       "hidden3d" accepts a list of parameters to control how hidden surfaces are plotted (or
       not) in 3D. It accepts a boolean argument indicating whether to hide "hidden" surfaces and
       lines; or a list ref containing parameters that control how hidden surfaces and lines are
       handled.  For details see the gnuplot manual.

       "xyplane" sets the location of that plane (which is drawn) relative to the rest of the
       plot in 3-space.  It takes a single string: "at" or "relative", and a number.
       "xyplane=>[at=>$z]" places the XY plane at the stated Z value (in scientific units) on the
       plot.  "xyplane=>[relative=>$frac]" places the XY plane $frac times the length of the
       scaled Z axis *below* the Z axis (i.e. 0 places it at the bottom of the plotted Z axis;
       and -1 places it at the top of the plotted Z axis).

       "mapping" takes a single string: "cartesian", "spherical", or "cylindrical".  It
       determines the interpretation of data coordinates in 3-space. (Compare to the "polar"
       option in 2-D).

   POs for Contour plots - contour, cntrparam
       Contour plots are only implemented in 3D.  To make a normal 2D contour plot, use 3-D mode,
       but set the view to "map" - which projects the 3-D plot onto its 2-D XY plane. (This is
       convoluted, for sure -- future versions of this module may have a cleaner way to do it).

       "contour" enables contour drawing on surfaces in 3D.  It takes a single string, which
       should be "base", "surface", or "both".

       "cntrparam" manages how contours are generated and smoothed.  It accepts a list ref with a
       collection of Gnuplot parameters that are issued one per line; refer to the Gnuplot manual
       for how to operate it.

   POs for Polar plots - polar, angles, mapping
       You can make 2-D polar plots by setting "polar" to a true value.  The ordinate is then
       plotted as angle, and the abscissa is radius on the plot.  The ordinate can be in either
       radians or degrees, depending on the "angles" parameter

       "angles" takes either "degrees" or "radians" (default is radians).

       "mapping" is used to set 3-D polar plots, either cylindrical or spherical (see the section
       on 3-D plotting, above).

   POs for Markup - label, arrow, object
       You specify plot markup in advance of the plot command, with plot options (or add it later
       with the "replot" method).  The options give you access to a collection of (separately)
       numbered descriptions that are accumulated into the plot object.  To add a markup object
       to the next plot, supply the appropriate options as a list ref or as a single string.  To
       specify all markup objects at once, supply the appropriate options for all of them as a
       nested list-of-lists.

       To modify an object, you can specify it by number, either by appending the number to the
       plot option name (e.g. "arrow3") or by supplying it as the first element of the option
       list for that object.

       To remove all objects of a given type, supply undef (e.g. "arrow=>undef").

       For example, to place two labels, use the plot option:

        label => [["Upper left",at=>"10,10"],["lower right",at=>"20,5"]];

       To add a label to an existing plot object, if you don't care about what index number it
       gets, do this:

        $w->options( label=>["my new label",at=>[10,20]] );

       If you do care what index number it gets (or want to replace an existing label), do this:

        $w->options( label=>[$n, "my replacement label", at=>"10,20"] );

       where $w is a Gnuplot object and $n contains the label number you care about.

       label - add a text label to the plot.

       The "label" option allows adding small bits of text at arbitrary locations on the plot.

       Each label specifier list ref accepts the following suboptions, in order.  All of them are
       optional -- if no options other than the index tag are given, then any existing label with
       that index is deleted.

       For examples, please refer to the Gnuplot 4.4 manual, p. 117.

       <tag> - optional index number (integer)
       <label text> - text to place on the plot.
          You may supply double-quotes inside the string, but it is not necessary in most cases
          (only if the string contains just an integer and you are not specifying a <tag>.

       at <position> - where to place the text (sci. coordinates)
          The <position> should be a string containing a gnuplot position specifier.  At its
          simplest, the position is just two numbers separated by a comma, as in
          "label2=>["foo",at=>"5,3"]", to specify (X,Y) location on the plot in scientific
          coordinates.  Each number can be preceded by a coordinate system specifier; see the
          Gnuplot 4.4 manual (page 20) for details.

       ( left | center | right ) - text placement rel. to position
       rotate [ by <degrees> ] - text rotation
          If "rotate" appears in the list alone, then the label is rotated 90 degrees CCW
          (bottom-to-top instead of left-to-right).  The following "by" clause is optional.

       font "<name>,<size>" - font specifier
          The <name>,<size> must be double quoted in the string (this may be fixed in a future
          version), as in

           label3=>["foo",at=>"3,4",font=>'"Helvetica,18"']

       noenhanced - turn off gnuplot enhanced text processing (if enabled)
       ( front | back ) - rendering order (last or first)
       textcolor <colorspec>
       (point <pointstyle> | nopoint ) - control whether the exact position is marked
       offset <offset> - offfset from position (in points).

       arrow - place an arrow or callout line on the plot

       Works similarly to the "label" option, but with an arrow instead of text.

       The arguments, all of which are optional but which must be given in the order listed, are:

       from <position> - start of arrow line
          The <position> should be a string containing a gnuplot position specifier.  At its
          simplest, the position is just two numbers separated by a comma, as in
          "arrow2=>["foo",at=>"5,3"]", to specify (X,Y) location on the plot in scientific
          coordinates.  Each number can be preceded by a coordinate system specifier; see the
          Gnuplot 4.4 manual (page 20) for details.

       ( to | rto ) <position>  - end of arrow line
          These work like "from".  For absolute placement, use "to".  For placement relative to
          the "from" position, use "rto".

       (arrowstyle | as) <arrow_style>
          This specifies that the arrow be drawn in a particular predeclared numerical style.  If
          you give this parameter, you should omit all the following ones.

       ( nohead | head | backhead | heads ) - specify arrowhead placement
       size <length>,<angle>,<backangle> - specify arrowhead geometry
       ( filled | empty | nofilled ) - specify arrowhead fill
       ( front | back ) - specify drawing order ( last | first )
       linestyle <line_style> - specify a numeric linestyle
       linetype <line_type> - specify numeric line type
       linewidth <line_width> - multiplier on the width of the line

       object - place a shape on the graph

       "object"s are rectangles, ellipses, circles, or polygons that can be placed arbitrarily on
       the plotting plane.

       The arguments, all of which are optional but which must be given in the order listed, are:

       <object-type> <object-properties> - type name of the shape and its type-specific
       properties
          The <object-type> is one of four words: "rectangle", "ellipse", "circle", or "polygon".

          You can specify a rectangle with "from=>$pos1, [r]to=>$pos2", with "center=>$pos1,
          size=>"$w,$h"", or with "at=>$pos1,size=>"$w,$h"".

          You can specify an ellipse with "at=>$pos, size=>"$w,$h"" or "center=>$pos,
          size=>"$w,$h"", followed by "angle=>$a".

          You can specify a circle with "at=>$pos," or "center=>$pos,", followed by
          "size=>$radius" and (optionally) "arc=>"[$begin:$end]"".

          You can specify a polygon with "from=>$pos1,to=>$pos2,to=>$pos3,...to=>$posn" or with
          "from=>$pos1,rto=>$diff1,rto=>$diff2,...rto=>$diffn".

       ( front | back | behind ) - draw the object last | first | really-first.
       fc <colorspec> - specify fill color
       fs <fillstyle> - specify fill style
       lw <width> - multiplier on line width

   POs for appearance tweaks - bars, boxwidth, isosamples, pointsize, style
       "bars" sets the width and behavior of the tick marks at the ends of error bars.  It takes
       a list containing at most two elements, both of which are optional:

       ·  A width specifier, which should be a numeric size multiplier times the usual width
          (which is about one character width in the default font size), or the word "fullwidth"
          to make the ticks the same width as their associated boxes in boxplots and histograms.

       ·  the word "front" or "back" to indicate drawing order in plots that might contain filled
          rectangles (e.g. boxes, candlesticks, or histograms).

       If you pass in the undefined value you get no ticks on errorbars; if you pass in the empty
       list ref you get default ticks.

       "boxwidth" sets the width of drawn boxes in boxplots, candlesticks, and histograms.  It
       takes a list containing at most two elements:

       ·  a numeric width

       ·  one of the words "absolute" or "relative".

       Unless you set "relative", the numeric width sets the width of boxes in X-axis scientific
       units (on log scales, this is measured at x=1 and the same width is used throughout the
       plot plane).  If "relative" is included, the numeric width is taken to be a multiplier on
       the default width.

       "isosamples" sets isoline density for plotting functions as surfaces.  You supply one or
       two numbers.  The first is the number of iso-u lines and the second is the number of iso-v
       lines.  If you only specify one, then the two are taken to be the same.  From the gnuplot
       manual: "An isoline is a curve parameterized by one of the surface parameters while the
       other surface parameter is fixed.  Isolines provide a simple means to display a surface.
       By fixing the u parameter of surface s(u,v), the iso-u lines of the form c(v) = s(u0,v)
       are produced, and by fixing the v parameter, the iso-v lines of the form c(u)=s(u,v0) are
       produced".

       "pointsize" accepts a single number and scales the size of points used in plots.

       "style" provides a great deal of customization for individual plot styles.  It is not
       (yet) fully parsed by PDL::Graphics::Gnuplot; please refer to the Gnuplot manual for
       details (it is pp. 145ff in the Gnuplot 4.6.1 maual).  "style" accepts a hash ref whose
       keys are plot styles (such as you would feed to the "with" curve option), and whose values
       are list refs containing keywords and other parameters to modify how each plot style
       should be displayed.

   POs for locale/internationalization - locale, decimalsign
       "locale" is used to control date stamp creation.  See the gnuplot manual.

       "decimalsign"  accepts a character to use in lieu of a "." for the decimalsign.  (e.g. in
       European countries use "decimalsign=>','").

       "globalwith" is used as a default plot style if no valid 'with' curve option is present
       for a given curve.

       If set to a nonzero value, "timestamp" causes a time stamp to be placed on the side of the
       plot, e.g. for keeping track of drafts.

       "zero" sets the approximation threshold for zero values within gnuplot.  Its default is
       1e-8.

       "fontpath" sets a font search path for gnuplot.  It accepts a collection of file names as
       a list ref.

   POs for advanced Gnuplot tweaks: topcmds, extracmds, bottomcmds, binary, dump, tee
       Plotting is carried out by sending a collection of commands to an underlying gnuplot
       process.  In general, the plot options cause "set" commands to be sent, configuring
       gnuplot to make the plot; these are followed by a "plot" or "splot" command and by any
       cleanup that is necessary to keep gnuplot in a known state.

       Provisions exist for sending commands directly to Gnuplot as part of a plot.  You can send
       commands at the top of the configuration but just under the initial "set terminal" and
       "set output" commands (with the "topcmds" option), at the bottom of the configuration and
       just before the "plot" command (with the "extracmds" option), or after the plot command
       (with the "bottomcmds" option).  Each of these plot options takes a list ref, each element
       of which should be one command line for gnuplot.

       Most plotting is done with binary data transfer to Gnuplot; however, due to some bugs in
       Gnuplot binary handling, certain types of plot data are sent in ASCII.  In particular,
       time series and label data require transmission in ASCII (as of Gnuplot 4.4).  You can
       force ASCII transmission of all but image data by explicitly setting the "binary=>0"
       option.

       "dump" is used for debugging. If true, it writes out the gnuplot commands to STDOUT
       instead of writing to a gnuplot process. Useful to see what commands would be sent to
       gnuplot. This is a dry run. Note that if the 'binary' option is given (see below), then
       this dump will contain binary data. If this binary data should be suppressed from the
       dump, set "dump => 'nobinary'".

       "tee" is used for debugging. If true, writes out the gnuplot commands to STDERR in
       addition to writing to a gnuplot process. This is not a dry run: data is sent to gnuplot
       and to the log. Useful for debugging I/O issues. Note that if the 'binary' option is given
       (see below), then this log will contain binary data. If this binary data should be
       suppressed from the log, set "tee => 'nobinary'".

CURVE OPTIONS

       The curve options describe details of specific curves within a plot.  They are in a hash,
       whose keys are as follows:

       legend
         Specifies the legend label for this curve

       axes
         Lets you specify which X and/or Y axes to plot on.  Gnuplot supports a main and
         alternate X and Y axis.  You specify them as a packed string with the x and y axes
         indicated: for example, "x1y1" to plot on the main axes, or "x1y2" to plot using an
         alternate Y axis (normally gridded on the right side of the plot).

       with
         Specifies the plot style for this curve. The value is passed to gnuplot using its 'with'
         keyword, so valid values are whatever gnuplot supports.  See above ("Plot styles
         supported") for a list of supported curve styles.

         The following curve options in this list modify the plot style further.  Not all of them
         are applicable to all plot styles -- for example, it makes no sense to specify a fill
         style for "with=>lines".

         For historical reasons, you can supply the with modifier curve options as a single
         string in the "with" curve option.  That usage is deprecated and will disappear in a
         future version of PDL::Graphics::Gnuplot.

       linetype (abbrev 'lt')
         This is a numeric selector from the default collection of line styles.  It includes
         automagic selection of dash style, color, and width from the default set of linetypes
         for your current output terminal.

       dashtype (abbrev 'dt')
         This is can be either a numeric type selector (0 for no dashes) or an ARRAY ref
         containing a list of up to 5 pairs of (dash length, space length).  The "dashtype" curve
         option is only supported for Gnuplot versions 5.0 and above.

         If you don't specify a "dashtype" curve option, the default behavior matches the
         behavior of earlier gnuplots: many terminals support a "dashed" terminal/output option,
         and if you have set that option (with the constructor or with the "output" method) then
         lines are uniquely dashed by default.  To make a single curve solid, specify "dt="0> as
         a curve option for it; or to make all curves solid, use the constructor or the "output"
         method to set the terminal option "dashed="0>.

         If your gnuplot is older than v5.0, the dashtype curve option is ignored (and causes a
         warning to be emitted).

       linestyle (abbrev 'ls')
         This works exactly like "linetype" above, except that you can modify individual line
         styles by setting the "style line <num>" plot option.  That is handy for a custom style
         you might use across several curves either a single plot or several plots.

       linewidth (abbrev 'lw')
         This is a numeric multiplier on the usual default line width in your current terminal.

       linecolor (abbrev 'lc')
         This is a color specifier for the color of the line.  You can feed in a standard color
         name (they're listed in the package-global variable
         @PDL::Graphics::Gnuplot::colornames), a small integer to index the standard linetype
         colors, the word "variable" to indicate that the line color is a standard linetype color
         to be drawn from an additional column of data, "[rgbcolor=><num>]" to specify an RGB
         color as a 24-bit packed integer, "[rgbcolor=>'variable']" to specify an additional
         column of data containing 24-bit packed integers with RGB color values,
         "[palette=>'frac',<val>]" to specify a single fractional position (scaled 0-1) in the
         current palette, or "[palette=>'cb',<val>]" to specify a single value in the scaled
         cbrange.

         There is no "linecolor=>[palette=>variable]" due to Gnuplot's non-orthogonal syntax.  To
         draw line color from the palette, via an additional data column, see the separate
         "palette" curve option (below).

       textcolor (abbrev 'tc')
         For plot styles like "labels" that specify text, this sets the color of the text.  It
         has the same format as "linecolor" (above).

       pointtype (abbrev 'pt')
         Selects a point glyph shape from the built-in list for your terminal, for plots that
         render points as small glyphs (like "points" and "linespoints").

       pointsize (abbrev 'ps')
         Selects a fractional size for point glyphs, relative to the default size on your
         terminal, for plots that render points as small glyphs.

       fillstyle (abbrev 'fs')
         Specify the way that filled regions should be colored, in plots that have fillable areas
         (like "boxes").  Unlike "linestyle" above, "fillstyle" accepts a full specification
         rather than an index into a set of predefined styles. You can feed in: 'empty' for no
         fill; 'transparent solid <density>' for a solid fill with optional <density> from 0.0 to
         1.0 (default 1.0); 'transparent pattern <n>' for a pattern fill--plotting multiple
         datasets causes the pattern to cycle through all available pattern types, starting from
         pattern <n> (be aware that the default <n>=0 may be equivalent to 'empty'); The
         'transparent' portions of the strings are optional, and are only effective on terminals
         that support transparency. Be aware that the quality of the visual output may depend on
         terminal type and rendering software.

         Any of those fill style specification strings can have a border specification string
         appended to it.  To specify a border, append 'border', and then optionally either
         'lt=><type>' or 'lc=><colorspec>' to the string.  To specify no border, append
         'noborder'.

       nohidden3d
         If you are making a 3D plot and have used the plot option "hidden3d" to get hidden line
         removal, you can override that for a particular curve by setting the "nohidden3d" option
         to a true value.  Only the single curve with "nohidden3d" set will have its hidden
         points rendered.

       nocontours
         If you are making a contour 3D plot, you can inhibit rendering of contours for a
         particular curve by setting "nocontours" to a true value.

       nosurface
         If you are making a surface 3D plot, you can inhibit rendering of the surface associated
         with a particular curve, by setting "nosurface" to a true value.

       palette
         Setting "palette => 1" causes line color to be drawn from an additional column in the
         data tuple.  This column is always the very last column in the tuple, in case of
         conflict (e.g. if you set both "pointsize=>variable" and "palette=>1", then the palette
         column is the last column and the pointsize column is second-to-last).

       tuplesize
         Specifies how many values represent each data point.  Normally you don't need to set
         this as individual "with" styles implicitly set a tuple size (which is automatically
         extended if you specify additional modifiers such as "palette" that require more data);
         this option lets you override PDL::Graphics::Gnuplot's parsing in case of irregularity.

       cdims
         Specifies the dimensions of of each column in this curve's tuple.  It must be 0, 1, or
         2.   Normally you don't need to set this for most plots; the main use is to specify that
         a 2-D data PDL is to be interpreted as a collection of 1-D columns rather than a single
         2-D grid (which would be the default in a 3-D plot). For example:

             $w=gpwin();
             $r2 = rvals(21,21)**2;
             $w->plot3d( wi=>'lines', xvals($r2), yvals($r2), $r2 );

         will produce a grid of values on a paraboloid. To instead plot a collection of lines
         using the threaded syntax, try

             $w->plot3d( wi=>'lines', cd=>1, xvals($r2), yvals($r2), $r2 );

         which will plot 21 separate curves in a threaded manner.

RECIPES

       Most of these come directly from Gnuplot commands. See the Gnuplot docs for details.

   2D plotting
       If we're plotting a piddle $y of y-values to be plotted sequentially (implicit domain),
       all you need is

         gplot($y);

       If we also have a corresponding $x domain, we can plot $y vs. $x with

         gplot($x, $y);

       Simple style control

       To change line thickness:

         gplot(with => 'lines',linewidth=>4, $x, $y);
         gplot(with => 'lines', lw=>4, $x, $y);

       To change point size and point type:

         gplot(with => 'points',pointtype=>8, $x, $y);
         gplot(with => 'points',pt=>8, $x, $y);

       Errorbars

       To plot errorbars that show $y +- 1, plotted with an implicit domain

         gplot(with => 'yerrorbars', $y, $y->ones);

       Same with an explicit $x domain:

         gplot(with => 'yerrorbars', $x, $y, $y->ones);

       Symmetric errorbars on both x and y. $x +- 1, $y +- 2:

         gplot(with => 'xyerrorbars', $x, $y, $x->ones, 2*$y->ones);

       To plot asymmetric errorbars that show the range $y-1 to $y+2 (note that here you must
       specify the actual errorbar-end positions, NOT just their deviations from the center; this
       is how Gnuplot does it)

         gplot(with => 'yerrorbars', $y, $y - $y->ones, $y + 2*$y->ones);

       More multi-value styles

       Plotting with variable-size circles (size given in plot units, requires Gnuplot >= 4.4)

         gplot(with => 'circles', $x, $y, $radii);

       Plotting with a variably-sized arbitrary point type (size given in multiples of the
       "default" point size)

         gplot(with => 'points', pointtype=>7, pointsize=>'variable',
               $x, $y, $sizes);

       Color-coded points

         gplot(with => 'points', palette=>1,
               $x, $y, $colors);

       Variable-size AND color-coded circles. A Gnuplot (4.4.0) bug make it necessary to specify
       the color range here

         gplot(cbmin => $mincolor, cbmax => $maxcolor,
               with => 'circles', palette=>1,
               $x, $y, $radii, $colors);

   3D plotting
       General style control works identically for 3D plots as in 2D plots.

       To plot a set of 3d points, with a square aspect ratio (squareness requires Gnuplot >=
       4.4):

         splot(square => 1, $x, $y, $z);

       If $xy is a 2D piddle, we can plot it as a height map on an implicit domain

         splot($xy);

       Complicated 3D plot with fancy styling:

         my $pi    = 3.14159;
         my $theta = zeros(200)->xlinvals(0, 6*$pi);
         my $z     = zeros(200)->xlinvals(0, 5);

         splot(title => 'double helix',

               { with => 'linespoints',
                 pointsize=>'variable',
                 pointtype=>7,
                 palette=>1,
                 legend => 'spiral 1' },
               { legend => 'spiral 2' },

               # 2 sets of x, 2 sets of y, single z
               PDL::cat( cos($theta), -cos($theta)),
               PDL::cat( sin($theta), -sin($theta)),
               $z,

               # pointsize, color
               0.5 + abs(cos($theta)), sin(2*$theta) );

       3D plots can be plotted as a heat map.

         splot( extracmds => 'set view 0,0',
                with => 'image',
                $xy );

   Hardcopies
       To send any plot to a file, instead of to the screen, one can simply do

         gplot(hardcopy => 'output.pdf',
               $x, $y);

       The "hardcopy" option is a shorthand for the "terminal" and "output" options. The output
       device is chosen from the file name suffix.

       If you want more (any) control over the output options (e.g. page size, font, etc.) then
       you can specify the output device using the "output" method or the constructor itself --
       or the corresponding plot options in the non-object mode. For example, to generate a PDF
       of a particular size with a particular font size for the text, one can do

         gplot(terminal => 'pdfcairo solid color font ",10" size 11in,8.5in',
               output   => 'output.pdf',
               $x, $y);

       This command is equivalent to the "hardcopy" shorthand used previously, but the fonts and
       sizes can be changed.

       Using the object oriented mode, you could instead say:

         $w = gpwin();
         $w->plot( $x, $y );
         $w->output( pdfcairo, solid=>1, color=>1,font=>',10',size=>[11,8.5,'in'] );
         $w->replot();
         $w->close();

       Many hardcopy output terminals (such as "pdf" and "svg") will not dump their plot to the
       file unless the file is explicitly closed with a change of output device or a call to
       "reset", "restart", or "close".  This is because those devices support multipage output
       and also require and end-of-file marker to close the file.

Plotting examples

   A simple example
          my $win = gpwin('x11');
          $win->plot( sin(xvals(45)) * 3.14159/10 );

       Here we just plot a simple function.  The default plot style is a line.  Line plots take a
       2-tuple (X and Y values).  Since we have supplied only one element, "plot()" understands
       it to be the Y value (abscissa) of the plot, and supplies value indices as X values -- so
       we get a plot of just over 2 cycles of the sine wave over an X range across X values from
       0 to 44.

   A not-so-simple example
          $win = gpwin('x11');
          $pi = 3.14159;
          $win->plot( {with => line}, xvals(10)**2, xvals(10),
                      {with => circles}, 2 * xvals(50), 2 * sin(xvals(50) * $pi / 10), xvals(50)/20
           );

       This plots sqrt(x) in an interesting way, and overplots some circles of varying size.  The
       line plot accepts a 2-tuple, and we supply both X and Y.  The circles plot accepts a
       3-tuple: X, Y, and R.

   A complicated example:
          $pi    = 3.14159;
          $theta = xvals(201) * 6 * $pi / 200;
          $z     = xvals(201) * 5 / 200;

          gplot( {trid => 1, title => 'double helix',cbr=>[0,1]},
                {with => 'linespoints',
                 pointsize=>'variable',
                 pointtype=>2,
                 palette=>1,
                 legend => ['spiral 1','spiral 2'],
                 cdim=>1},
                pdl( cos($theta), -cos($theta) ),       # x
                pdl( sin($theta), -sin($theta) ),       # y
                $z,                                     # z
                (0.5 + abs(cos($theta))),               # pointsize
                sin($theta/3),                          # color
                { with=>'points',
                  pointsize=>'variable',
                  pointtype=>5,
                  palette=>0
                },
                zeroes(6),                         # x
                zeroes(6),                         # y
                xvals(6),                          # z
                xvals(6)+1                         # point size
          );

       This is a 3d plot with variable size and color. There are 5 values in the tuple.  The
       first 2 piddles have dimensions (N,2); all the other piddles have a single dimension. The
       "cdim=>1" specifies that each column of data should be one-dimensional. Thus the PDL
       threading generates 2 distinct curves, with varying values for x,y and identical values
       for everything else.  To label the curves differently, 2 different sets of curve options
       are given.  Omitting the "cdim" curve option would yield a 201x2 grid with the
       "linespoints" plotstyle, rather than two separate curves.

       In addition to the threaded pair of linespoints curves, there are six variable size points
       plotted as filled squares, as a secondary curve.

       Plot options are passed in in two places:  as a leading hash ref, and as a trailing hash
       ref.  Any other hash elements or hash refs must be curve options.

       Curves are delimited by non-data arguments.  After the initial hash ref, curve options for
       the first curve (the threaded pair of spirals) are passed in as a second hash ref.  The
       curve's data arguments are ended by the first non-data argument (the hash ref with the
       curve options for the second curve).

FUNCTIONS

   gpwin
        use PDL::Graphics::Gnuplot;
        $w = gpwin( @options );
        $w->plot( @plot_args );

       gpwin is the PDL::Graphics::Gnuplot exported constructor.  It is exported by default and
       is a synonym for "new PDL::Graphics::Gnuplot(...)".  If given no arguments, it creates a
       plot object with the default terminal settings for your gnuplot.  You can also give it the
       name of a Gnuplot terminal type (e.g. 'x11') and some terminal and output options (see
       "output").

   new
           $w = new PDL::Graphics::Gnuplot;
           $w->plot( @plot_args );
           #
           # Specify plot options alone
           $w = new PDL::Graphics::Gnuplot( {%plot_options} );
           #
           # Specify device and device options (and optional default plot options)
           $w = new PDL::Graphics::Gnuplot( device, %device_options, {%plot_options} );
           $w->plot( @plot_args );

       Creates a PDL::Graphics::Gnuplot persistent plot object, and connects it to gnuplot.

       For convenience, you can specify the output device and its options right here in the
       constructor.  Because different gnuplot devices accept different options, you must specify
       a device if you want to specify any device configuration options (such as window size,
       output file, text mode, or default font).

       If you don't specify a device type, then the Gnuplot default device for your system gets
       used.  You can set that with an environment variable (check the Gnuplot documentation).

       Gnuplot uses the word "terminal" for output devices; you can see a list of terminals
       supported by PDL::Graphics::Gnuplot by invoking "PDL::Graphics::Gnuplot::terminfo()" (for
       example in the perldl shell).

       For convenience, you can provide default plot options here.  If the last argument to
       "new()" is a trailing hash ref, it is treated as plot options.

       After you have created an object, you can change its terminal/output device with the
       "output" method, which is useful for (e.g.) throwing up an interactive plot and then
       sending it to a hardcopy device. See "output" for a description of terminal options and
       how to format them.

       Normally, the object connects to the command "gnuplot" in your path, using the
       "Alien::Gnuplot" module.  If you need to specify a binary other than this default, check
       the "Alien::Gnuplot" documentation.

         my $plot = PDL::Graphics::Gnuplot->new({title => 'Object-oriented plot'});
         $plot->plot( legend => 'curve', sequence(5) );

   output
           $window->output( $device );
           $window->output( $device, %device_options );
           $window->output( $device, %device_options, {plot_options} );
           $window->output( %device_options, {plot_options} );
           $window->output( %device_options );

       Sets the output device and options for a Gnuplot object. If you omit the $device name,
       then you get the gnuplot default device (generally "x11", "wxt", or "aqua", depending on
       platform).

       You can control the output device of a PDL::Graphics::Gnuplot object on the fly.  That is
       useful, for example, to replot several versions of the same plot to different output
       devices (interactive and hardcopy).

       Gnuplot interprets terminal options differently per device.  PDL::Graphics::Gnuplot
       attempts to interpret some of the more common ones in a common way.  In particular:

       size
          Most drivers support a "size" option to specify the size of the output plotting
          surface.  The format is [$width, $height, $unit]; the trailing unit string is optional
          but recommended, since the default unit of length changes from device to device.

          The unit string can be in, cm, mm, px, char, or pt.  Pixels are taken to be 1 point in
          size (72 pixels per inch) and dimensions are computed accordingly.  Characters are
          taken to be 12 point in size (6 per inch).

       output
          This option actually sets the object's "output" option for most terminal devices; that
          changes the file to which the plot will be written.  Some devices, notably X11 and
          Aqua, don't make proper use of "output"; for those devices, specifying "output" in the
          object constructor actually sets the appropriate terminal option (e.g. "window" in the
          X11 terminal).  This is described as a "plot option" in the Gnuplot manual, but it is
          treated as a setup variable and parsed with the setup/terminal options here in the
          constructor.

          If you don't specify an output device, plots will go to sequentially-numbered files of
          the form "Plot-<n>.<suf>" in your current working directory.  In that case,
          PDL::Graphics::Gnuplot will report (on STDERR) where the plot ended up.

       enhanced
          This is a flag that indicates whether to enable Gnuplot's enhanced text processing
          (e.g. for superscripts and subscripts).  Set it to a false value for plain text, to a
          true value for enhanced text (which includes LaTeX-like markup for super/sub scripts
          and fonts).

       For a brief description of the terminal options that any one device supports, you can run
       PDL::Graphics::Gnuplot::terminfo().

       As with plot options, terminal options can be abbreviated to the shortest unique string --
       so (e.g.) "size" can generally be abbreviated "si" and "monochrome" can be abbreviated
       "mono" or "mo".

   close
         $w=gpwin();
         $w->plot(xvals(5));
         $w->close;

       Close gnuplot process (actually just a synonym for restart)

       Some of the gnuplot terminals (e.g. pdf) don't write out a file promptly.  The close
       method closes the associated gnuplot subprocess, forcing the file to be written out.  It
       is implemented as a simple restart operation.

       The object preserves the plot state, so "replot" and similar methods still work with the
       new subprocess.

   restart
           $w->restart();
           PDL::Graphics::Gnuplot::restart();

       Restart the gnuplot backend for a plot object

       Occasionally the gnuplot backend can get into an unknown state.  "restart" kills the
       gnuplot backend and starts a new one, preserving state in the object.  (i.e. "replot" and
       similar functions work even with the new subprocess).

       Called with no arguments, "restart" applies to the global plot object.

   reset
           $w->reset()

       Clear state from the gnuplot backend

       Clears all plot option state from the underlying object.  All plot options except
       "terminal", "termoptions", "output", and "multiplot" are cleared.  This is similar to the
       "reset" command supported by gnuplot itself, and in fact it also causes a "reset" to be
       sent to gnuplot.

   options
         $w = new PDL::Graphics::Gnuplot();
         $w->options( globalwith=>'lines' );
         print %{$w->options()};

       Set/get persistent plot options for a plot object

       The options method parses plot options into a gnuplot object on a cumulative basis, and
       returns the resultant options hash.

       If called as a sub rather than a method, options() changes the global gnuplot object.

   gplot
       Plot method exported by default (synonym for "PDL::Graphics::Gnuplot::plot")

   plot
       This is the main plotting routine in PDL::Graphics::Gnuplot.

       Each "plot()" call creates a new plot from whole cloth, either creating or overwriting the
       output for that device.

       If you want to add features to an existing plot, use "replot".

       "plot()" understands the PDL bad value mechanism.  Bad values are omitted from the plot.

        $w=gpwin();
        $w->plot({temp_plot_options},                 # optional
             curve_options, data, data, ... ,      # curve_options are optional for the first plot
             curve_options, data, data, ... ,
              {temp_plot_options});

       Most of the arguments are optional.

       All of the extensive array of gnuplot plot styles are supported, including images and 3-D
       plots.

        use PDL::Graphics::Gnuplot qw(plot);
        my $x = sequence(101) - 50;
        plot($x**2);

       See main POD for PDL::Graphics::Gnuplot for details.

       You can pass plot options into plot as either a leading or trailing hash ref, or both.  If
       you pass both, the trailing hash ref is parsed last and overrides the leading hash.

       For debugging and curiosity purposes, the last plot command issued to gnuplot is
       maintained in a package global: $PDL::Graphics::Gnuplot::last_plotcmd, and also in each
       object as the {last_plotcmd} field.

   replot
       Replot the last plot (possibly with new arguments).

       "replot" is similar to gnuplot's "replot" command - it allows you to regenerate the last
       plot made with this object.  You can change the plot by adding new elements to it,
       modifying options, or even (with the "device" method) changing the output device.
       "replot" takes the same arguments as "plot".

       If you give no arguments at all (or only a plot object) then the plot is simply redrawn.
       If you give plot arguments, they are added to the new plot exactly as if you'd included
       them in the original plot element list, and maintained for subsequent replots.

       (Compare to 'markup').

   markup
       Add ephemeral markup to the last plot.

       "markup" works exactly the same as "replot", except that any new arguments are not added
       to the replot list - so you can add temporary markup to a plot and regenerate the plot
       later without it.

   plot3d
       Generate 3D plots. Synonym for "plot(trid => 1, ...)"

   splot
       Generate 3D plots.  Synonym for "plot(trid => 1, ...)"

   lines
       Generates plots with lines, by default. Shorthand for "plot(globalwith => 'lines', ...)"

   points
       Generates plots with points, by default. Shorthand for "plot(globalwith => 'points', ...)"

   image
       Displays an image (either greyscale or RGB).  Shorthand for "plot(globalwith => 'image',
       ...)"

   imag
       Synonym for "image", for people who grew up with PDL::Graphics::PGPLOT and can't remember
       the closing 'e'

   fits
       Displays a FITS image.  Synonym for "plot(globalwith => 'fits', ...)".

   multiplot
        $a = (xvals(101)/100) * 6 * 3.14159/180;
        $b = sin($a);

        $w->multiplot(layout=>[2,2,"columnsfirst"]);
        $w->plot({title=>"points"},with=>"points",$a,$b);
        $w->plot({title=>"lines"}, with=>"lines", $a,$b);
        $w->plot({title=>"image"}, with=>"image", $a->(*1) * $b );
        $w->end_multi();

       Plot multiple plots into a single page of output.

       The "multiplot" method enables multiplot mode in gnuplot, which permits multiple plots on
       a single pane.  Plots can be lain out in a grid, or can be lain out freeform using the
       "size" and "origin" plot options for each of the individual plots.

       It is not possible to change the terminal or output device when in multiplot mode; if you
       try to do that, by setting one of those plot options, PDL::Graphics::Gnuplot will throw an
       error.

       The options hash will accept:

       layout - define a regular grid of plots to multiplot
          "layout" should be followed by an ARRAY ref that contains at least number of columns
          ("NX") followed by number of rows ("NY).  After that, you may include any of the
          "rowsfirst", "columnsfirst", "downwards", or "upwards" keywords to specify traversal
          order through the grid.  Only the first letter is examined, so (e.g.) "down" or even
          "dog" works the same as "downwards".

       title - define a title for the entire page
          "title" should be followed by a single scalar containing the title string.

       scale - make gridded plots larger or smaller than their allocated space
          "scale" takes either a scalar or a list ref containing one or two values.  If only one
          value is supplied, it is a general scale factor of each plot in the grid.  If two
          values are supplied, the first is an X stretch factor for each plot in the grid, and
          the second is a Y stretch factor for each plot in the grid.

       offset - offset each plot from its grid origin
          "offset" takes a list ref containing two values, that control placement of each plot
          within the grid.

   end_multi
        $w=gpwin();
        $w->multiplot(layout=>[2,1]);
        $w->plot({title=>"points},with=>'points',$a,$b);
        $w->plot({title=>"lines",with=>"lines",$a,$b);
        $w->end_multi();

       Ends a multiplot block (i.e. a block of plots that are meant to render to a single page).

   read_mouse
         ($x,$y,$char,$modstring) = $w->read_mouse($message);
         $hash = $w->read_mouse($message);

       Get a mouse click or keystroke from the active interactive plot window.

       For interactive devices (e.g. x11, wxt, aqua), read_mouse lets you accept a keystroke or
       mouse button input from the gnuplot window.  In list context, it returns four arguments
       containing the reported X, Y, keystroke character, and modifiers packed in a string.  In
       scalar context, it returns a hash ref containing those things.

       read_mouse blocks execution for input, but responds gracefully to interrupts.

   read_polygon
         $points = $w->read_polygon(%opt)

       Read in a polygon by accepting mouse clicks.  The polygon is returned as a 2xN PDL of
       ($x,$y) values in scientific units. Acceptable options are:

       message - what to print before collecting points
          There are some printf-style escapes for the prompt:

          * %c - expands to "an open" or "a closed"

          * %n - number of points currently in the polygon

          * %N - number of points expected for the polygon

          * %k - list of all keys accepted

          * "%%" - %

       prompt  - what to print to prompt the user for the next point
          "prompt" uses the same escapes as "message".

       n_points - number of points to accept (or 0 for indefinite)
          With 0 value, points are accepted until the user presses 'q' or 'ESC' on the keyboard
          with focus on the graph.  With other value, points are accepted until that happens *or*
          until the number of points is at least n_points.

       actions - hash of callback code refs indexed by character for action
          You can optionally call a callback routine when any particular character is pressed.
          The actions table is a hash ref whose keys are characters and whose values are either
          code refs (to be called on the associated keypress) or array refs containing a short
          description string followed by a code ref.  Non-printable characters (e.g. ESC, BS,
          DEL) are accessed via a hash followed by a three digit decimal ASCII code -- e.g.
          "#127" for DEL. Button events are indexed with the strings "BUTTON1", "BUTTON2", and
          "BUTTON3", and modifications must be entered as well for shift, control, and

          The code ref receives the arguments ($obj, $c, $poly,$x,$y,$mods), where:

          $obj is the plot object
          $c is the character (or "BUTTON"n"" string),
          $poly is a scalar ref; $$poly is the current polygon before the action,
          $x and $y are the current scientific coordinates, and
          $mods is the modifier string.
            You can't override the 'q' or '#027' (ESC) callbacks.  You *can* override the BUTTON1
            and DEL callbacks, potentially preventing the user from entering points at all!  You
            should do that with caution.

          closed - (default false): generate a closed polygon
            This works by duplicating the initial point at the end of the point list.

          markup - (default 'linespoints'): style to use to render the polygon on the fly
            If this is set to a true value, it should be a valid 'with' specifier (curve option).
            The routine will call markup after each click.

   terminfo
           use PDL::Graphics::Gnuplot qw/terminfo/;
           terminfo();        # print info about all known terminals
           terminfo 'aqua';   # print info about the aqua terminal

           $w = gpwin();
           $w->terminfo();

       Print out information about gnuplot terminals and their custom option syntax.

       The "terminfo" routine is a reference tool to describe the Gnuplot terminal types and the
       options they accept.  It's mainly useful in interactive sessions.  It outputs information
       directly to the terminal.

COMPATIBILITY

       Everything should work on all platforms that support Gnuplot and Perl.  Currently, MacOS,
       Fedora and Debian Linux, Cygwin, and Microsoft Windows (under both Active State Strawberry
       Perl) have been tested to work, although the interprocess control link is not as reliable
       under Microsoft Windows as under POSIX systems.  Please report successes or failures on
       other platforms to the authors. A transcript of a failed run with {tee => 1} would be most
       helpful.

REPOSITORY

       <https://github.com/drzowie/PDL-Graphics-Gnuplot>

AUTHOR

       Craig DeForest, "<craig@deforest.org>" and Dima Kogan, "<dima@secretsauce.net>"

STILL TO DO

       some plot and curve options need better parsing:
          - labels need attention (plot option labels)
             They need to be handled as hashes, not just as array refs.  Also, they don't seem to
             be working with timestamps.  Further, deeply nested options (e.g. "at" for labels)
             need attention.

       - new plot styles
          The "boxplot" plot style (new to gnuplot 4.6?) requires a different using syntax and
          will require some hacking to support.

LICENSE AND COPYRIGHT

       Copyright 2011-2013 Craig DeForest and Dima Kogan

       This program is free software; you can redistribute it and/or modify it under the terms of
       either: the GNU General Public License 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.