@c Copyright (C) 1996-2015 John W. Eaton
@c
@c This file is part of Octave.
@c
@c Octave is free software; you can redistribute it and/or modify it
@c under the terms of the GNU General Public License as published by the
@c Free Software Foundation; either version 3 of the License, or (at
@c your option) any later version.
@c
@c Octave is distributed in the hope that it will be useful, but WITHOUT
@c ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
@c FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
@c for more details.
@c
@c You should have received a copy of the GNU General Public License
@c along with Octave; see the file COPYING.  If not, see
@c <http://www.gnu.org/licenses/>.

@node Plotting
@chapter Plotting
@cindex plotting
@cindex graphics

@menu
* Introduction to Plotting::
* High-Level Plotting::
* Graphics Data Structures::
* Advanced Plotting::
@end menu

@node Introduction to Plotting
@section Introduction to Plotting

Earlier versions of Octave provided plotting through the use of
gnuplot.  This capability is still available.  But, a newer plotting
capability is provided by access to OpenGL@.  Which plotting system
is used is controlled by the @code{graphics_toolkit} function.
@xref{Graphics Toolkits}.

The function call @code{graphics_toolkit ("fltk")} selects the
FLTK/OpenGL system, and @code{graphics_toolkit ("gnuplot")} selects the
gnuplot system.  The two systems may be used selectively through the use
of the @code{graphics_toolkit} property of the graphics handle for each
figure.  This is explained in @ref{Graphics Data Structures}.
@strong{Caution:} The FLTK toolkit uses single precision variables internally
which limits the maximum value that can be displayed to approximately
@math{10^{38}}.  If your data contains larger values you must use the gnuplot
toolkit which supports values up to @math{10^{308}}.

@node High-Level Plotting
@section High-Level Plotting
@cindex plotting, high-level

Octave provides simple means to create many different types of two- and
three-dimensional plots using high-level functions.

If you need more detailed control, see @ref{Graphics Data Structures}
and @ref{Advanced Plotting}.

@menu
* Two-Dimensional Plots::
* Three-Dimensional Plots::
* Plot Annotations::
* Multiple Plots on One Page::
* Multiple Plot Windows::
* Manipulation of Plot Objects::
* Manipulation of Plot Windows::
* Use of the @code{interpreter} Property::
* Printing and Saving Plots::
* Interacting with Plots::
* Test Plotting Functions::
@end menu

@node Two-Dimensional Plots
@subsection Two-Dimensional Plots

@menu
* Axis Configuration::
* Two-dimensional Function Plotting::
* Two-dimensional Geometric Shapes::
@end menu

The @code{plot} function allows you to create simple x-y plots with
linear axes.  For example,

@example
@group
x = -10:0.1:10;
plot (x, sin (x));
@end group
@end example

@noindent
displays a sine wave shown in @ref{fig:plot}.  On most systems, this
command will open a separate plot window to display the graph.

@float Figure,fig:plot
@center @image{plot,4in}
@caption{Simple Two-Dimensional Plot.}
@end float

@DOCSTRING(plot)

The @code{plotyy} function may be used to create a plot with two
independent y axes.

@DOCSTRING(plotyy)

The functions @code{semilogx}, @code{semilogy}, and @code{loglog} are
similar to the @code{plot} function, but produce plots in which one or
both of the axes use log scales.

@DOCSTRING(semilogx)

@DOCSTRING(semilogy)

@DOCSTRING(loglog)

The functions @code{bar}, @code{barh}, @code{stairs}, and @code{stem}
are useful for displaying discrete data.  For example,

@example
@group
hist (randn (10000, 1), 30);
@end group
@end example

@noindent
produces the histogram of 10,000 normally distributed random numbers
shown in @ref{fig:hist}.

@float Figure,fig:hist
@center @image{hist,4in}
@caption{Histogram.}
@end float

@DOCSTRING(bar)

@DOCSTRING(barh)

@DOCSTRING(hist)

@DOCSTRING(stemleaf)

@DOCSTRING(printd)

@DOCSTRING(stairs)

@DOCSTRING(stem)

@DOCSTRING(stem3)

@DOCSTRING(scatter)

@DOCSTRING(plotmatrix)

@DOCSTRING(pareto)

@DOCSTRING(rose)

The @code{contour}, @code{contourf} and @code{contourc} functions
produce two-dimensional contour plots from three-dimensional data.

@DOCSTRING(contour)

@DOCSTRING(contourf)

@DOCSTRING(contourc)

@DOCSTRING(contour3)

The @code{errorbar}, @code{semilogxerr}, @code{semilogyerr}, and
@code{loglogerr} functions produce plots with error bar markers.  For
example,

@example
@group
x = 0:0.1:10;
y = sin (x);
lerr = 0.1 .* rand (size (x));
uerr = 0.1 .* rand (size (x));
errorbar (x, y, lerr, uerr);
@end group
@end example

@noindent
produces the figure shown in @ref{fig:errorbar}.

@float Figure,fig:errorbar
@center @image{errorbar,4in}
@caption{Errorbar plot.}
@end float

@DOCSTRING(errorbar)

@DOCSTRING(semilogxerr)

@DOCSTRING(semilogyerr)

@DOCSTRING(loglogerr)

Finally, the @code{polar} function allows you to easily plot data in
polar coordinates.  However, the display coordinates remain rectangular
and linear.  For example,

@example
polar (0:0.1:10*pi, 0:0.1:10*pi);
@end example

@noindent
produces the spiral plot shown in @ref{fig:polar}.

@float Figure,fig:polar
@center @image{polar,4in}
@caption{Polar plot.}
@end float

@DOCSTRING(polar)

@DOCSTRING(pie)

@DOCSTRING(pie3)

@DOCSTRING(quiver)

@DOCSTRING(quiver3)

@DOCSTRING(compass)

@DOCSTRING(feather)

@DOCSTRING(pcolor)

@DOCSTRING(area)

@DOCSTRING(fill)

@DOCSTRING(comet)

@DOCSTRING(comet3)

@DOCSTRING(frame2im)

@DOCSTRING(im2frame)

@node Axis Configuration
@subsubsection Axis Configuration

The axis function may be used to change the axis limits of an existing
plot and various other axis properties, such as the aspect ratio and the
appearance of tic marks.

@DOCSTRING(axis)

Similarly the axis limits of the colormap can be changed with the caxis
function.

@DOCSTRING(caxis)

The @code{xlim}, @code{ylim}, and @code{zlim} functions may be used to
get or set individual axis limits.  Each has the same form.

@c Add cross-references and function index entries for other limit functions.
@anchor{XREFylim}
@anchor{XREFzlim}
@findex ylim
@findex zlim
@DOCSTRING(xlim)

@node Two-dimensional Function Plotting
@subsubsection Two-dimensional Function Plotting
@cindex plotting, two-dimensional functions

Octave can plot a function from a function handle, inline function, or
string defining the function without the user needing to explicitly
create the data to be plotted.  The function @code{fplot} also generates
two-dimensional plots with linear axes using a function name and limits
for the range of the x-coordinate instead of the x and y data.  For
example,

@example
@group
fplot (@@sin, [-10, 10], 201);
@end group
@end example

@noindent
produces a plot that is equivalent to the one above, but also includes a
legend displaying the name of the plotted function.

@DOCSTRING(fplot)

Other functions that can create two-dimensional plots directly from a
function include @code{ezplot}, @code{ezcontour}, @code{ezcontourf} and
@code{ezpolar}.

@DOCSTRING(ezplot)

@DOCSTRING(ezcontour)

@DOCSTRING(ezcontourf)

@DOCSTRING(ezpolar)

@node Two-dimensional Geometric Shapes
@subsubsection Two-dimensional Geometric Shapes

@DOCSTRING(rectangle)

@node Three-Dimensional Plots
@subsection Three-Dimensional Plots
@cindex plotting, three-dimensional

The function @code{mesh} produces mesh surface plots.  For example,

@example
@group
tx = ty = linspace (-8, 8, 41)';
[xx, yy] = meshgrid (tx, ty);
r = sqrt (xx .^ 2 + yy .^ 2) + eps;
tz = sin (r) ./ r;
mesh (tx, ty, tz);
@end group
@end example

@noindent
produces the familiar ``sombrero'' plot shown in @ref{fig:mesh}.  Note
the use of the function @code{meshgrid} to create matrices of X and Y
coordinates to use for plotting the Z data.  The @code{ndgrid} function
is similar to @code{meshgrid}, but works for N-dimensional matrices.

@float Figure,fig:mesh
@center @image{mesh,4in}
@caption{Mesh plot.}
@end float

The @code{meshc} function is similar to @code{mesh}, but also produces a
plot of contours for the surface.

The @code{plot3} function displays arbitrary three-dimensional data,
without requiring it to form a surface.  For example,

@example
@group
t = 0:0.1:10*pi;
r = linspace (0, 1, numel (t));
z = linspace (0, 1, numel (t));
plot3 (r.*sin(t), r.*cos(t), z);
@end group
@end example

@noindent
displays the spiral in three dimensions shown in @ref{fig:plot3}.

@float Figure,fig:plot3
@center @image{plot3,4in}
@caption{Three-dimensional spiral.}
@end float

Finally, the @code{view} function changes the viewpoint for
three-dimensional plots.

@DOCSTRING(mesh)

@DOCSTRING(meshc)

@DOCSTRING(meshz)

@DOCSTRING(hidden)

@DOCSTRING(surf)

@DOCSTRING(surfc)

@DOCSTRING(surfl)

@DOCSTRING(surfnorm)

@DOCSTRING(isosurface)

@DOCSTRING(isonormals)

@DOCSTRING(isocolors)

@DOCSTRING(shrinkfaces)

@DOCSTRING(diffuse)

@DOCSTRING(specular)

@DOCSTRING(meshgrid)

@DOCSTRING(ndgrid)

@DOCSTRING(plot3)

@DOCSTRING(view)

@DOCSTRING(slice)

@DOCSTRING(ribbon)

@DOCSTRING(shading)

@DOCSTRING(scatter3)

@DOCSTRING(waterfall)

@menu
* Aspect Ratio::
* Three-dimensional Function Plotting::
* Three-dimensional Geometric Shapes::
@end menu

@node Aspect Ratio
@subsubsection Aspect Ratio

For three-dimensional plots the aspect ratio can be set for data with
@code{daspect} and for the plot box with @code{pbaspect}.
@xref{Axis Configuration}, for controlling the x-, y-, and z-limits for
plotting.

@DOCSTRING(daspect)

@DOCSTRING(pbaspect)

@node Three-dimensional Function Plotting
@subsubsection Three-dimensional Function Plotting

@DOCSTRING(ezplot3)

@DOCSTRING(ezmesh)

@DOCSTRING(ezmeshc)

@DOCSTRING(ezsurf)

@DOCSTRING(ezsurfc)

@node Three-dimensional Geometric Shapes
@subsubsection Three-dimensional Geometric Shapes

@DOCSTRING(cylinder)

@DOCSTRING(sphere)

@DOCSTRING(ellipsoid)

@node Plot Annotations
@subsection Plot Annotations

You can add titles, axis labels, legends, and arbitrary text to an
existing plot.  For example:

@example
@group
x = -10:0.1:10;
plot (x, sin (x));
title ("sin(x) for x = -10:0.1:10");
xlabel ("x");
ylabel ("sin (x)");
text (pi, 0.7, "arbitrary text");
legend ("sin (x)");
@end group
@end example

The functions @code{grid} and @code{box} may also be used to add grid
and border lines to the plot.  By default, the grid is off and the
border lines are on.

Finally, arrows, text and rectangular or elliptic boxes can be added to
highlight parts of a plot using the @code{annotation} function.  Those objects
are drawn in an invisible axes, on top of every other axes.

@DOCSTRING(title)

@DOCSTRING(legend)

@DOCSTRING(text)

See @ref{Text Properties} for the properties that you can set.

@anchor{XREFylabel}
@anchor{XREFzlabel}
@DOCSTRING(xlabel)

@DOCSTRING(clabel)

@DOCSTRING(box)

@DOCSTRING(grid)

@DOCSTRING(colorbar)

@DOCSTRING(annotation)

@node Multiple Plots on One Page
@subsection Multiple Plots on One Page
@cindex plotting, multiple plots per figure

Octave can display more than one plot in a single figure.  The simplest
way to do this is to use the @code{subplot} function to divide the plot
area into a series of subplot windows that are indexed by an integer.
For example,

@example
@group
subplot (2, 1, 1)
fplot (@@sin, [-10, 10]);
subplot (2, 1, 2)
fplot (@@cos, [-10, 10]);
@end group
@end example

@noindent
creates a figure with two separate axes, one displaying a sine wave and
the other a cosine wave.  The first call to subplot divides the figure
into two plotting areas (two rows and one column) and makes the first plot
area active.  The grid of plot areas created by @code{subplot} is
numbered in column-major order (top to bottom, left to right).

@DOCSTRING(subplot)

@node Multiple Plot Windows
@subsection Multiple Plot Windows
@cindex plotting, multiple plot windows

You can open multiple plot windows using the @code{figure} function.
For example,

@example
@group
figure (1);
fplot (@@sin, [-10, 10]);
figure (2);
fplot (@@cos, [-10, 10]);
@end group
@end example

@noindent
creates two figures, with the first displaying a sine wave and
the second a cosine wave.  Figure numbers must be positive integers.

@DOCSTRING(figure)

@node Manipulation of Plot Objects
@subsection Manipulation of Plot Objects
@cindex plotting, object manipulation

@DOCSTRING(pan)

@DOCSTRING(rotate)

@DOCSTRING(rotate3d)

@DOCSTRING(zoom)

@node Manipulation of Plot Windows
@subsection Manipulation of Plot Windows
@cindex plotting, window manipulation

By default, Octave refreshes the plot window when a prompt is printed,
or when waiting for input.  The
@code{drawnow} function is used to cause a plot window to be updated.

@DOCSTRING(drawnow)

Only figures that are modified will be updated.  The @code{refresh}
function can also be used to cause an update of the current figure, even if
it is not modified.

@DOCSTRING(refresh)

Normally, high-level plot functions like @code{plot} or @code{mesh} call
@code{newplot} to initialize the state of the current axes so that the
next plot is drawn in a blank window with default property settings.  To
have two plots superimposed over one another, use the @code{hold}
function.  For example,

@example
@group
hold on;
x = -10:0.1:10;
plot (x, sin (x));
plot (x, cos (x));
hold off;
@end group
@end example

@noindent
displays sine and cosine waves on the same axes.  If the hold state is
off, consecutive plotting commands like this will only display the last
plot.

@DOCSTRING(newplot)

@DOCSTRING(hold)

@DOCSTRING(ishold)
To clear the current figure, call the @code{clf} function.  To clear the
current axis, call the @code{cla} function.  To bring the current figure
to the top of the window stack, call the @code{shg} function.  To delete
a graphics object, call @code{delete} on its index.  To close the
figure window, call the @code{close} function.

@DOCSTRING(clf)

@DOCSTRING(cla)

@DOCSTRING(shg)

@DOCSTRING(delete)

@DOCSTRING(close)

@DOCSTRING(closereq)

@node Use of the @code{interpreter} Property
@subsection Use of the @code{interpreter} Property

All text objects---such as titles, labels, legends, and text---include
the property @qcode{"interpreter"} that determines the manner in
which special control sequences in the text are rendered.

The interpreter property can take three values: @qcode{"none"}, @qcode{"tex"},
@qcode{"latex"}.  If the interpreter is set to @qcode{"none"} then no special
rendering occurs---the displayed text is a verbatim copy of the specified text.
Currently, the @qcode{"latex"} interpreter is not implemented and is equivalent
to @qcode{"none"}.

The @qcode{"tex"} option implements a subset of @TeX{} functionality when
rendering text.  This allows the insertion of special glyphs such as Greek
characters or mathematical symbols.  Special characters are inserted by using
a backslash (\) character followed by a code, as shown in @ref{tab:extended}.

Note that for on-screen display the interpreter property is honored by all
graphics toolkits.  However for printing, @strong{only} the @qcode{"gnuplot"}
toolkit renders @TeX{} instructions.

Besides special glyphs, the formatting of the text can be changed within the
string by using the codes

@multitable @columnfractions .2 .2 .6 .2
@item @tab \bf @tab Bold font @tab
@item @tab \it @tab Italic font @tab
@item @tab \sl @tab Oblique Font @tab
@item @tab \rm @tab Normal font @tab
@end multitable

These codes may be used in conjunction with the @{ and @} characters to limit
the change to a part of the string.  For example,

@example
xlabel ('@{\bf H@} = a @{\bf V@}')
@end example

@noindent
where the character @qcode{'a'} will not appear in bold font.  Note that to
avoid having Octave interpret the backslash character in the strings,
the strings themselves should be in single quotes.

It is also possible to change the fontname and size within the text

@multitable @columnfractions .1 .4 .6 .1
@item @tab \fontname@{@var{fontname}@} @tab Specify the font to use @tab
@item @tab \fontsize@{@var{size}@} @tab Specify the size of the font to
use @tab
@end multitable

The color of the text may also be changed inline using either a string (e.g.,
"red") or numerically with a Red-Green-Blue (RGB) specification (.e.g.,
[1 0 0], also red).

@multitable @columnfractions .1 .4 .6 .1
@item @tab \color@{@var{color}@} @tab Specify the color as a string @tab
@item @tab \color[rgb]@{@var{R} @var{G} @var{B}@} @tab Specify the color
numerically @tab
@end multitable

Finally, superscripting and subscripting can be controlled with the @qcode{'^'}
and @qcode{'_'} characters.  If the @qcode{'^'} or @qcode{'_'} is followed by a
@{ character, then all of the block surrounded by the @{ @} pair is
superscripted or subscripted.  Without the @{ @} pair, only the character
immediately following the @qcode{'^'} or @qcode{'_'} is changed.

@float Table,tab:extended
@tex
\vskip 6pt
\newdimen\cola \cola=78pt
\newdimen\colb \colb=78pt
\newdimen\colc \colc=78pt
\def\symtable#1#2#3{
\hbox to \hsize {\hfill\vbox{\offinterlineskip \tabskip=0pt
\hskip36pt #1
\vskip6pt
\halign{
\vrule height2.0ex depth1.ex width 0.6pt #2\tabskip=0.3em &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule
width 0.6pt \tabskip=0pt\cr
\noalign{\hrule height 0.6pt}
& Code && Sym && Code && Sym && Code && Sym &\cr
\noalign{\hrule}
#3
\noalign{\hrule height 0.6pt}
}
}\hfill}}
\hoffset72pt
\symtable{Greek Lowercase Letters} {#}
{& \hbox to \cola{$\backslash$alpha }    && $\alpha$
&& \hbox to \colb{$\backslash$beta }     && $\beta$
&& \hbox to \colc{$\backslash$gamma}     && $\gamma$     &\cr
& $\backslash$delta      && $\delta$
&& $\backslash$epsilon   && $\epsilon$
&& $\backslash$zeta      && $\zeta$      &\cr
& $\backslash$eta        && $\eta$
&& $\backslash$theta     && $\theta$
&& $\backslash$vartheta  && $\vartheta$  &\cr
& $\backslash$iota       && $\iota$
&& $\backslash$kappa     && $\kappa$
&& $\backslash$lambda    && $\lambda$    &\cr
& $\backslash$mu         && $\mu$
&& $\backslash$nu        && $\nu$
&& $\backslash$xi        && $\xi$        &\cr
& $\backslash$o          && $o$
&& $\backslash$pi        && $\pi$
&& $\backslash$varpi     && $\varpi$     &\cr
& $\backslash$rho        && $\rho$
&& $\backslash$sigma     && $\sigma$
&& $\backslash$varsigma  && $\varsigma$  &\cr
& $\backslash$tau        && $\tau$
&& $\backslash$upsilon   && $\upsilon$
&& $\backslash$phi       && $\phi$       &\cr
& $\backslash$chi        && $\chi$
&& $\backslash$psi       && $\psi$
&& $\backslash$omega     && $\omega$     &\cr}
\vskip12pt
\symtable{Greek Uppercase Letters} {#}
{& \hbox to \cola{$\backslash$Gamma}   && $\Gamma$
&& \hbox to \colb{$\backslash$Delta}   && $\Delta$
&& \hbox to \colc{$\backslash$Theta}   && $\Theta$      &\cr
& $\backslash$Lambda   && $\Lambda$
&& $\backslash$Xi      && $\Xi$
&& $\backslash$Pi      && $\Pi$         &\cr
& $\backslash$Sigma    && $\Sigma$
&& $\backslash$Upsilon && $\Upsilon$
&& $\backslash$Phi     && $\Phi$        &\cr
& $\backslash$Psi      && $\Psi$
&& $\backslash$Omega   && $\Omega$
&&    &&       &\cr}
\vskip12pt
\symtable{Misc Symbols Type Ord} {#}
{& \hbox to \cola{$\backslash$aleph}       && $\aleph$
&& \hbox to \colb{$\backslash$wp}          && $\wp$
&& \hbox to \colc{$\backslash$Re}          && $\Re$      &\cr
& $\backslash$Im           && $\Im$
&& $\backslash$partial     && $\partial$
&& $\backslash$infty       && $\infty$       &\cr
& $\backslash$prime        && $\prime$
&& $\backslash$nabla       && $\nabla$
&& $\backslash$surd        && $\surd$        &\cr
& $\backslash$angle        && $\angle$
&& $\backslash$forall      && $\forall$
&& $\backslash$exists      && $\exists$      &\cr
& $\backslash$neg          && $\neg$
&& $\backslash$clubsuit    && $\clubsuit$
&& $\backslash$diamondsuit && $\diamondsuit$ &\cr
& $\backslash$heartsuit    && $\heartsuit$
&& $\backslash$spadesuit   && $\spadesuit$
&&    &&       &\cr}
\vskip12pt
\symtable{``Large'' Operators} {#}
{& \hbox to \cola{$\backslash$int}   && $\int$
&& \hbox to \colb{}   &&
&& \hbox to \colc{}   &&       &\cr}
\vskip12pt
\symtable{Binary operators} {#}
{& \hbox to \cola{$\backslash$pm}     && $\pm$
&& \hbox to \colb{$\backslash$cdot}   && $\cdot$
&& \hbox to \colc{$\backslash$times}  && $\times$      &\cr
& $\backslash$ast     && $\ast$
&& $\backslash$circ   && $\circ$
&& $\backslash$bullet && $\bullet$     &\cr
& $\backslash$div     && $\div$
&& $\backslash$cap    && $\cap$
&& $\backslash$cup    && $\cup$        &\cr
& $\backslash$vee     && $\vee$
&& $\backslash$wedge  && $\wedge$
&& $\backslash$oplus  && $\oplus$      &\cr
& $\backslash$otimes  && $\otimes$
&& $\backslash$oslash && $\oslash$
&&    &&      &\cr}
@end tex
@ifnottex
@multitable @columnfractions .25 .25 .25 .25
@item Greek Lowercase Letters
@item @tab  \alpha      @tab  \beta        @tab  \gamma
@item @tab  \delta      @tab  \epsilon     @tab  \zeta
@item @tab  \eta        @tab  \theta       @tab  \vartheta
@item @tab  \iota       @tab  \kappa       @tab  \lambda
@item @tab  \mu         @tab  \nu          @tab  \xi
@item @tab  \o          @tab  \pi          @tab  \varpi
@item @tab  \rho        @tab  \sigma       @tab  \varsigma
@item @tab  \tau        @tab  \upsilon     @tab  \phi
@item @tab  \chi        @tab  \psi         @tab  \omega
@item Greek Uppercase Letters
@item @tab  \Gamma      @tab  \Delta       @tab  \Theta
@item @tab  \Lambda     @tab  \Xi          @tab  \Pi
@item @tab  \Sigma      @tab  \Upsilon     @tab  \Phi
@item @tab  \Psi        @tab  \Omega       @tab
@item Misc Symbols Type Ord
@item @tab  \aleph      @tab  \wp          @tab  \Re
@item @tab  \Im         @tab  \partial     @tab  \infty
@item @tab  \prime      @tab  \nabla       @tab  \surd
@item @tab  \angle      @tab  \forall      @tab  \exists
@item @tab  \neg        @tab  \clubsuit    @tab  \diamondsuit
@item @tab  \heartsuit  @tab  \spadesuit   @tab
@item ``Large'' Operators
@item @tab  \int
@item Binary Operators
@item @tab  \pm         @tab  \cdot        @tab  \times
@item @tab  \ast        @tab  \circ        @tab  \bullet
@item @tab  \div        @tab  \cap         @tab  \cup
@item @tab  \vee        @tab  \wedge       @tab  \oplus
@item @tab  \otimes     @tab  \oslash      @tab
@item Relations
@item @tab  \leq        @tab  \subset      @tab  \subseteq
@item @tab  \in         @tab  \geq         @tab  \supset
@item @tab  \supseteq   @tab  \ni          @tab  \mid
@item @tab  \equiv      @tab  \sim         @tab  \approx
@item @tab  \cong       @tab  \propto      @tab  \perp
@item Arrows
@item @tab  \leftarrow  @tab  \Leftarrow   @tab  \rightarrow
@item @tab  \Rightarrow @tab  \leftrightarrow @tab  \uparrow
@item @tab  \downarrow  @tab               @tab
@item Openings and Closings
@item @tab  \lfloor     @tab  \langle      @tab  \lceil
@item @tab  \rfloor     @tab  \rangle      @tab  \rceil
@item Alternate Names
@item @tab  \neq
@item Other
@item @tab  \ldots      @tab  \0          @tab  \copyright
@item @tab  \deg
@end multitable
@end ifnottex
@caption{Available special characters in @TeX{} mode}
@end float
@float
@tex
\vskip 6pt
\newdimen\cola \cola=78pt
\newdimen\colb \colb=78pt
\newdimen\colc \colc=78pt
\def\symtable#1#2#3{\hbox to \hsize {\hfill\vbox{\offinterlineskip \tabskip=0pt
\hskip36pt #1
\vskip6pt
\halign{
\vrule height2.0ex depth1.ex width 0.6pt #2\tabskip=0.3em &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule &
#2 \hfil & \vrule #2 & #2 \hfil & #2 \vrule
width 0.6pt \tabskip=0pt\cr
\noalign{\hrule height 0.6pt}
& Code && Sym && Code && Sym && Code && Sym &\cr
\noalign{\hrule}
#3
\noalign{\hrule height 0.6pt}
}
}\hfill}}
\hoffset72pt
\vskip12pt
\symtable{Relations} {#}
{& \hbox to \cola{$\backslash$leq}      && $\leq$
&& \hbox to \colb{$\backslash$subset}   && $\subset$
&& \hbox to \colc{$\backslash$subseteq} && $\subseteq$    &\cr
& $\backslash$in        && $\in$
&& $\backslash$geq      && $\geq$
&& $\backslash$supset   && $\supset$      &\cr
& $\backslash$supseteq  && $\supseteq$
&& $\backslash$ni       && $\ni$
&& $\backslash$mid      && $\mid$         &\cr
& $\backslash$equiv     && $\equiv$
&& $\backslash$sim      && $\sim$
&& $\backslash$approx   && $\approx$      &\cr
& $\backslash$cong      && $\cong$
&& $\backslash$propto   && $\propto$
&& $\backslash$perp     && $\perp$        &\cr}
\vskip12pt
\symtable{Arrows} {#}
{& \hbox to \cola{$\backslash$leftarrow}      && $\leftarrow$
&& \hbox to \colb{$\backslash$Leftarrow}      && $\Leftarrow$
&& \hbox to \colc{$\backslash$rightarrow}     && $\rightarrow$      &\cr
& $\backslash$Rightarrow      && $\Rightarrow$
&& $\backslash$leftrightarrow && $\leftrightarrow$
&& $\backslash$uparrow        && $\uparrow$         &\cr
& $\backslash$downarrow       && $\downarrow$
&&   &&
&&   &&       &\cr}
\vskip12pt
\symtable{Openings and Closings} {#}
{& \hbox to \cola{$\backslash$lfloor   }    && $\lfloor$
&& \hbox to \colb{$\backslash$langle   }    && $\langle$
&& \hbox to \colc{$\backslash$lceil    }    && $\lceil$      &\cr
& $\backslash$rfloor    && $\rfloor$
&& $\backslash$rangle   && $\rangle$
&& $\backslash$rceil    && $\rceil$      &\cr}
\vskip12pt
\symtable{Alternate Names} {#}
{& \hbox to \cola{$\backslash$neq}   && $\neq$
&& \hbox to \colb{}   &&
&& \hbox to \colc{}   &&   &\cr}
\vskip12pt
\symtable{Other (not in Appendix F Tables)} {#}
{& \hbox to \cola{$\backslash$ldots}     && $\ldots$
&& \hbox to \colb{$\backslash$0}         && $\oslash$
&& \hbox to \colc{$\backslash$copyright} && $\copyright$      &\cr
& $\backslash$deg        && $^\circ$
&&    &&
&&    &&       &\cr}
\vskip12pt
\hskip36pt Table 15.1: Available special characters in \TeX\ mode (cont.)
@end tex
@end float

A complete example showing the capabilities of the extended text is

@example
@group
x = 0:0.01:3;
plot (x, erf (x));
hold on;
plot (x,x,"r");
axis ([0, 3, 0, 1]);
text (0.65, 0.6175, strcat ('\leftarrow x = @{2/\surd\pi',
' @{\fontsize@{16@}\int_@{\fontsize@{8@}0@}^@{\fontsize@{8@}x@}@}',
' e^@{-t^2@} dt@} = 0.6175'))
@end group
@end example

@ifnotinfo
@noindent
The result of which can be seen in @ref{fig:extendedtext}

@float Figure,fig:extendedtext
@center @image{extended,4in}
@caption{Example of inclusion of text with the @TeX{} interpreter}
@end float
@end ifnotinfo

@node Printing and Saving Plots
@subsection Printing and Saving Plots
@cindex plotting, saving and printing plots
@cindex printing plots
@cindex saving plots

The @code{print} command allows you to send plots to you printer and
to save plots in a variety of formats.  For example,

@example
print -dpsc
@end example

@noindent
prints the current figure to a color PostScript printer.  And,

@example
print -deps foo.eps
@end example

@noindent
saves the current figure to an encapsulated PostScript file called
@file{foo.eps}.

The different graphic toolkits have different print capabilities.  In
particular, the OpenGL based toolkits such as @code{fltk} do not support
the @qcode{"interpreter"} property of text objects.  This means special
symbols drawn with the @qcode{"tex"} interpreter will appear correctly
on-screen but will be rendered with interpreter @qcode{"none"} when printing.
Switch graphics toolkits for printing if this is a concern.

@DOCSTRING(print)

@DOCSTRING(saveas)

@DOCSTRING(orient)

@code{print} and @code{saveas} are used when work on a plot has finished
and the output must be in a publication-ready format.  During intermediate
stages it is often better to save the graphics object and all of its
associated information so that changes---to colors, axis limits, marker styles,
etc.---can be made easily from within Octave.  The @code{hgsave}/@code{hgload}
commands can be used to save and re-create a graphics object.

@DOCSTRING(hgsave)

@DOCSTRING(hgload)

@node Interacting with Plots
@subsection Interacting with Plots

The user can select points on a plot with the @code{ginput} function or
selection the position at which to place text on the plot with the
@code{gtext} function using the mouse.  Menus may also be created
and populated with specific user commands via the @code{uimenu} function.

@DOCSTRING(ginput)

@DOCSTRING(waitforbuttonpress)

@DOCSTRING(gtext)

@DOCSTRING(uimenu)

@node Test Plotting Functions
@subsection Test Plotting Functions

The functions @code{sombrero} and @code{peaks} provide a way to check
that plotting is working.  Typing either @code{sombrero} or @code{peaks}
at the Octave prompt should display a three-dimensional plot.

@DOCSTRING(sombrero)

@DOCSTRING(peaks)
@node Graphics Data Structures
@section Graphics Data Structures
@cindex graphics data structures

@menu
* Introduction to Graphics Structures::
* Graphics Objects::
* Graphics Object Properties::
* Searching Properties::
* Managing Default Properties::
@end menu

@node Introduction to Graphics Structures
@subsection Introduction to Graphics Structures
@cindex introduction to graphics structures
@anchor{XREFgraphics structures}

The graphics functions use pointers, which are of class graphics_handle, in
order to address the data structures which control visual display.  A
graphics handle may point to any one of a number of different base object
types and these objects are the graphics data structures themselves.  The
primitive graphic object types are: @code{figure}, @code{axes}, @code{line},
@code{text}, @code{patch}, @code{surface}, @code{text}, and @code{image}.

Each of these objects has a function by the same name, and, each of these
functions returns a graphics handle pointing to an object of the corresponding
type.  In addition there are several functions which operate on properties of
the graphics objects and which also return handles: the functions @code{plot}
and @code{plot3} return a handle pointing to an object of type line, the
function @code{subplot} returns a handle pointing to an object of type axes,
the function @code{fill} returns a handle pointing to an object of type patch,
the functions @code{area}, @code{bar}, @code{barh}, @code{contour},
@code{contourf}, @code{contour3}, @code{surf}, @code{mesh}, @code{surfc},
@code{meshc}, @code{errorbar}, @code{quiver}, @code{quiver3}, @code{scatter},
@code{scatter3}, @code{stair}, @code{stem}, @code{stem3} each return a handle
to a complex data structure as documented in
@ref{XREFdatasources,,Data Sources}.

The graphics objects are arranged in a hierarchy:

1. The root is at 0.  In other words, @code{get (0)} returns the properties of
the root object.

2. Below the root are @code{figure} objects.

3. Below the @code{figure} objects are @code{axes} objects.

4. Below the @code{axes} objects are @code{line}, @code{text}, @code{patch},
@code{surface}, and @code{image} objects.

Graphics handles may be distinguished from function handles
(@pxref{Function Handles}) by means of the function @code{ishandle}.
@code{ishandle} returns true if its argument is a handle of a graphics object.
In addition, a figure or axes object may be tested using @code{isfigure} or
@code{isaxes} respectively.  The test functions return true only if the
argument is both a handle and of the correct type (figure or axes).

The @code{whos} function can be used to show the object type of each currently
defined graphics handle.  (Note: this is not true today, but it is, I hope,
considered an error in whos.  It may be better to have whos just show
graphics_handle as the class, and provide a new function which, given a
graphics handle, returns its object type.  This could generalize the ishandle()
functions and, in fact, replace them.)

The @code{get} and @code{set} commands are used to obtain and set the values of
properties of graphics objects.  In addition, the @code{get} command may be
used to obtain property names.

For example, the property @qcode{"type"} of the graphics object pointed to by
the graphics handle h may be displayed by:

@example
get (h, "type")
@end example

The properties and their current values are returned by @code{get (h)}
where h is a handle of a graphics object.  If only the names of the
allowed properties are wanted they may be displayed by:
@code{get (h, "")}.

Thus, for example:

@smallexample
h = figure ();
get (h, "type")
ans = figure
get (h, "");
error: get: ambiguous figure property name ; possible matches:

__enhanced__           hittest                resize
__graphics_toolkit__   integerhandle          resizefcn
__guidata__            interruptible          selected
__modified__           inverthardcopy         selectionhighlight
__myhandle__           keypressfcn            selectiontype
__plot_stream__        keyreleasefcn          tag
alphamap               menubar                toolbar
beingdeleted           mincolormap            type
busyaction             name                   uicontextmenu
buttondownfcn          nextplot               units
children               numbertitle            userdata
clipping               outerposition          visible
closerequestfcn        paperorientation       windowbuttondownfcn
color                  paperposition          windowbuttonmotionfcn
colormap               paperpositionmode      windowbuttonupfcn
createfcn              papersize              windowkeypressfcn
currentaxes            papertype              windowkeyreleasefcn
currentcharacter       paperunits             windowscrollwheelfcn
currentobject          parent                 windowstyle
currentpoint           pointer                wvisual
deletefcn              pointershapecdata      wvisualmode
dockcontrols           pointershapehotspot    xdisplay
doublebuffer           position               xvisual
filename               renderer               xvisualmode
handlevisibility       renderermode
@end smallexample

The root figure has index 0.  Its properties may be displayed by:
@code{get (0, "")}.

The uses of @code{get} and @code{set} are further explained in
@ref{XREFget,,get}, @ref{XREFset,,set}.

@DOCSTRING(isprop)

@node Graphics Objects
@subsection Graphics Objects
@cindex graphics objects

The hierarchy of graphics objects was explained above.
@xref{Introduction to Graphics Structures}.  Here the
specific objects are described, and the properties contained in
these objects are discussed.  Keep in mind that
graphics objects are always referenced by @dfn{handle}.

@table @asis
@c @group

@item root figure
@cindex root figure graphics object
@cindex graphics object, root figure
the top level of the hierarchy and the parent of all figure objects.
The handle index of the root figure is 0.

@item figure
@cindex figure graphics object
@cindex graphics object, figure
A figure window.

@item axes
@cindex axes graphics object
@cindex graphics object, axes
A set of axes.  This object is a child of a figure object and may be a
parent of line, text, image, patch, or surface objects.

@item line
@cindex line graphics object
@cindex graphics object, line
A line in two or three dimensions.

@item text
@cindex text graphics object
@cindex graphics object, text
Text annotations.

@item image
@cindex image graphics object
@cindex graphics object, image
A bitmap image.

@item patch
@cindex patch graphics object
@cindex graphics object, patch
A filled polygon, currently limited to two dimensions.

@item surface
@cindex surface graphics object
@cindex graphics object, surface
A three-dimensional surface.
@c @end group
@end table

@subsubsection Creating Graphics Objects
@cindex creating graphics objects

You can create any graphics object primitive by calling the function of the
same name as the object; In other words, @code{figure}, @code{axes},
@code{line}, @code{text}, @code{image}, @code{patch}, and @code{surface}
functions.  These fundamental graphic objects automatically become children
of the current axes object as if @code{hold on} was in place.  Seperately, axes
will automatically become children of the current figure object and figures
will become children of the root object 0.

If this auto-joining feature is not desired then it is important to call
@code{newplot} first to prepare a new figure and axes for plotting.
Alternatively, the easier way is to call a high-level graphics routine which
will both create the plot and then populate it with low-level graphics objects.
Instead of calling @code{line}, use @code{plot}.  Or use @code{surf} instead of
@code{surface}.  Or use @code{fill} instead of @code{patch}.

@DOCSTRING(axes)

@DOCSTRING(line)

@DOCSTRING(patch)

@DOCSTRING(surface)

@subsubsection Handle Functions
@cindex handle functions

To determine whether a variable is a graphics object index, or an index
to an axes or figure, use the functions @code{ishandle}, @code{isaxes}, and
@code{isfigure}.

@DOCSTRING(ishandle)

@DOCSTRING(ishghandle)

@DOCSTRING(isaxes)

@DOCSTRING(isfigure)

The function @code{gcf} returns an index to the current figure object,
or creates one if none exists.  Similarly, @code{gca} returns the
current axes object, or creates one (and its parent figure object) if
none exists.

@DOCSTRING(gcf)

@DOCSTRING(gca)

@DOCSTRING(gco)

The @code{get} and @code{set} functions may be used to examine and set
properties for graphics objects.  For example,

@example
@group
get (0)
    @result{} ans =
       @{
         type = root
         currentfigure = [](0x0)
         children = [](0x0)
         visible = on
         @dots{}
       @}
@end group
@end example

@noindent
returns a structure containing all the properties of the root figure.
As with all functions in Octave, the structure is returned by value, so
modifying it will not modify the internal root figure plot object.  To
do that, you must use the @code{set} function.  Also, note that in this
case, the @code{currentfigure} property is empty, which indicates that
there is no current figure window.

The @code{get} function may also be used to find the value of a single
property.  For example,

@example
@group
get (gca (), "xlim")
    @result{} [ 0 1 ]
@end group
@end example

@noindent
returns the range of the x-axis for the current axes object in the
current figure.

To set graphics object properties, use the set function.  For example,

@example
set (gca (), "xlim", [-10, 10]);
@end example

@noindent
sets the range of the x-axis for the current axes object in the current
figure to @samp{[-10, 10]}.

Default property values can also be queried if the @code{set} function is
called without a value argument.  When only one argument is given (a graphic
handle) then a structure with defaults for all properties of the given object
type is returned.  For example,

@example
set (gca ())
@end example

@noindent
returns a structure containing the default property values for axes objects.
If @code{set} is called with two arguments (a graphic handle and a property
name) then only the defaults for the requested property are returned.

@DOCSTRING(get)

@DOCSTRING(set)

@DOCSTRING(ancestor)

@DOCSTRING(allchild)

@DOCSTRING(findfigs)

@cindex saving graphics objects
@cindex graphics objects, saving

Figures can be printed or saved in many graphics formats with @code{print} and
@code{saveas}.  Occasionally, however, it may be useful to save the original
Octave handle graphic directly so that further modifications can be made such
as modifying a title or legend.

This can be accomplished with the following functions by

@example
@group
fig_struct = hdl2struct (gcf);
save myplot.fig -struct fig_struct;
@dots{}
fig_struct = load ("myplot.fig");
struct2hdl (fig_struct);
@end group
@end example

@DOCSTRING(hdl2struct)

@DOCSTRING(struct2hdl)

@DOCSTRING(copyobj)

@node Graphics Object Properties
@subsection Graphics Object Properties
@cindex graphics object properties

@menu
* Root Figure Properties::
* Figure Properties::
* Axes Properties::
* Line Properties::
* Text Properties::
* Image Properties::
* Patch Properties::
* Surface Properties::
@end menu

In this Section the graphics object properties are discussed in detail, starting
with the root figure properties and continuing through the objects
hierarchy.  The documentation about a specific graphics object can be displayed
using @code{doc} function, e.g., @code{doc ("axes properties")} will show
@ref{Axes Properties}.

The allowed values for radio (string) properties can be retrieved
programmatically or displayed using the one or
two arguments call to @code{set} function.  @xref{XREFset, , set}.

In the following documentation, default values are enclosed in @{ @}.

@node Root Figure Properties
@subsubsection Root Figure Properties
@cindex root figure properties

The @code{root figure} properties are:

@include plot-rootproperties.texi


@node Figure Properties
@subsubsection Figure Properties
@cindex figure properties

The @code{figure} properties are:

@include plot-figureproperties.texi


@node Axes Properties
@subsubsection Axes Properties
@cindex axes properties

The @code{axes} properties are:

@include plot-axesproperties.texi


@node Line Properties
@subsubsection Line Properties
@cindex line properties

The @code{line} properties are:

@include plot-lineproperties.texi


@node Text Properties
@subsubsection Text Properties
@cindex text properties

The @code{text} properties are:

@include plot-textproperties.texi


@node Image Properties
@subsubsection Image Properties
@cindex image properties

The @code{image} properties are:

@include plot-imageproperties.texi


@node Patch Properties
@subsubsection Patch Properties
@cindex patch properties

The @code{patch} properties are:

@include plot-patchproperties.texi


@node Surface Properties
@subsubsection Surface Properties
@cindex surface properties

The @code{surface} properties are:

@include plot-surfaceproperties.texi


@node Searching Properties
@subsection Searching Properties

@DOCSTRING(findobj)

@DOCSTRING(findall)
@node Managing Default Properties
@subsection Managing Default Properties
@cindex default graphics properties
@cindex graphics properties, default

Object properties have two classes of default values, @dfn{factory
defaults} (the initial values) and @dfn{user-defined defaults}, which
may override the factory defaults.

Although default values may be set for any object, they are set in
parent objects and apply to child objects, of the specified object type.
For example, setting the default @code{color} property of @code{line}
objects to @qcode{"green"}, for the @code{root} object, will result in all
@code{line} objects inheriting the @code{color} @qcode{"green"} as the default
value.

@example
set (0, "defaultlinecolor", "green");
@end example

@noindent
sets the default line color for all objects.  The rule for constructing
the property name to set a default value is

@example
default + @var{object-type} + @var{property-name}
@end example

This rule can lead to some strange looking names, for example
@code{defaultlinelinewidth"} specifies the default @code{linewidth}
property for @code{line} objects.

The example above used the root figure object, 0, so the default
property value will apply to all line objects.  However, default values
are hierarchical, so defaults set in a figure objects override those
set in the root figure object.  Likewise, defaults set in axes objects
override those set in figure or root figure objects.  For example,

@example
@group
subplot (2, 1, 1);
set (0, "defaultlinecolor", "red");
set (1, "defaultlinecolor", "green");
set (gca (), "defaultlinecolor", "blue");
line (1:10, rand (1, 10));
subplot (2, 1, 2);
line (1:10, rand (1, 10));
figure (2)
line (1:10, rand (1, 10));
@end group
@end example

@noindent
produces two figures.  The line in first subplot window of the first
figure is blue because it inherits its color from its parent axes
object.  The line in the second subplot window of the first figure is
green because it inherits its color from its parent figure object.  The
line in the second figure window is red because it inherits its color
from the global root figure parent object.

To remove a user-defined default setting, set the default property to
the value @qcode{"remove"}.  For example,

@example
set (gca (), "defaultlinecolor", "remove");
@end example

@noindent
removes the user-defined default line color setting from the current axes
object.  To quickly remove all user-defined defaults use the @code{reset}
function.

@DOCSTRING(reset)

Getting the @qcode{"default"} property of an object returns a list of
user-defined defaults set for the object.  For example,

@example
get (gca (), "default");
@end example

@noindent
returns a list of user-defined default values for the current axes
object.

Factory default values are stored in the root figure object.  The
command

@example
get (0, "factory");
@end example

@noindent
returns a list of factory defaults.

@node Advanced Plotting
@section Advanced Plotting


@menu
* Colors::
* Line Styles::
* Marker Styles::
* Callbacks::
* Application-defined Data::
* Object Groups::
* Graphics Toolkits::
@end menu


@node Colors
@subsection Colors
@cindex graphics colors
@cindex colors, graphics

Colors may be specified as RGB triplets with values ranging from zero to
one, or by name.  Recognized color names include @qcode{"blue"},
@qcode{"black"}, @qcode{"cyan"}, @qcode{"green"}, @qcode{"magenta"},
@qcode{"red"}, @qcode{"white"}, and @qcode{"yellow"}.

@node Line Styles
@subsection Line Styles
@cindex line styles, graphics
@cindex graphics line styles

Line styles are specified by the following properties:

@table @code
@item linestyle
May be one of

@table @asis
@item @qcode{"-"}
Solid line.  [default]

@c Special handling required to avoid '--' becoming single en-dash in Info
@ifnottex

@item @verb{|"--"|}
@end ifnottex
@iftex

@item @code{"--"}
@end iftex
Dashed line.

@item @qcode{":"}
Dotted line.

@item @qcode{"-."}
A dash-dot line.

@item @qcode{"none"}
No line.  Points will still be marked using the current Marker Style.
@end table

@item linewidth
A number specifying the width of the line.  The default is 1.  A value
of 2 is twice as wide as the default, etc.
@end table

@node Marker Styles
@subsection Marker Styles
@cindex graphics marker styles
@cindex marker styles, graphics

Marker styles are specified by the following properties:

@table @code
@item marker
A character indicating a plot marker to be place at each data point, or
@qcode{"none"}, meaning no markers should be displayed.

@item markeredgecolor
The color of the edge around the marker, or @qcode{"auto"}, meaning that
the edge color is the same as the face color.  @xref{Colors}.

@item markerfacecolor
The color of the marker, or @qcode{"none"} to indicate that the marker
should not be filled.  @xref{Colors}.

@item markersize
A number specifying the size of the marker.  The default is 1.  A value
of 2 is twice as large as the default, etc.
@end table

The @code{colstyle} function will parse a @code{plot}-style specification
and will return the color, line, and marker values that would result.

@DOCSTRING(colstyle)

@node Callbacks
@subsection Callbacks
@cindex callbacks

Callback functions can be associated with graphics objects and triggered
after certain events occur.  The basic structure of all callback function
is

@example
@group
function mycallback (src, data)
@dots{}
endfunction
@end group
@end example

@noindent
where @code{src} gives a handle to the source of the callback, and
@code{code} gives some event specific data.  This can then be associated
with an object either at the objects creation or later with the
@code{set} function.  For example,

@example
plot (x, "DeleteFcn", @@(s, e) disp ("Window Deleted"))
@end example

@noindent
where at the moment that the plot is deleted, the message "Window
Deleted" will be displayed.

Additional user arguments can be passed to callback functions, and will
be passed after the 2 default arguments.  For example:

@example
@group
plot (x, "DeleteFcn", @{@@mycallback, "1"@})
@dots{}
function mycallback (src, data, a1)
  fprintf ("Closing plot %d\n", a1);
endfunction
@end group
@end example

The basic callback functions that are available for all graphics objects
are

@itemize @bullet
@item CreateFcn
This is the callback that is called at the moment of the objects
creation.  It is not called if the object is altered in any way, and so
it only makes sense to define this callback in the function call that
defines the object.  Callbacks that are added to @code{CreateFcn} later with
the @code{set} function will never be executed.

@item DeleteFcn
This is the callback that is called at the moment an object is deleted.

@item ButtonDownFcn
This is the callback that is called if a mouse button is pressed while
the pointer is over this object.  Note, that the gnuplot interface does
not respect this callback.
@end itemize

The object and figure that the event occurred in that resulted in the
callback being called can be found with the @code{gcbo} and @code{gcbf}
functions.

@DOCSTRING(gcbo)

@DOCSTRING(gcbf)

Callbacks can equally be added to properties with the @code{addlistener}
function described below.

@node Application-defined Data
@subsection Application-defined Data
@cindex application-defined data

Octave has a provision for attaching application-defined data to a graphics
handle.  The data can be anything which is meaningful to the application, and
will be completely ignored by Octave.

@DOCSTRING(setappdata)

@DOCSTRING(getappdata)

@DOCSTRING(rmappdata)

@DOCSTRING(isappdata)

@node Object Groups
@subsection Object Groups
@cindex object groups

A number of Octave high level plot functions return groups of other
graphics objects or they return graphics objects that have their
properties linked in such a way that changes to one of the properties
results in changes in the others.  A graphic object that groups other
objects is an @code{hggroup}

@DOCSTRING(hggroup)

For example a simple use of a @code{hggroup} might be

@example
@group
x = 0:0.1:10;
hg = hggroup ();
plot (x, sin (x), "color", [1, 0, 0], "parent", hg);
hold on
plot (x, cos (x), "color", [0, 1, 0], "parent", hg);
set (hg, "visible", "off");
@end group
@end example

@noindent
which groups the two plots into a single object and controls their
visibility directly.  The default properties of an @code{hggroup} are
the same as the set of common properties for the other graphics
objects.  Additional properties can be added with the @code{addproperty}
function.

@DOCSTRING(addproperty)

Once a property in added to an @code{hggroup}, it is not linked to any
other property of either the children of the group, or any other
graphics object.  Add so to control the way in which this newly added
property is used, the @code{addlistener} function is used to define a
callback function that is executed when the property is altered.

@DOCSTRING(addlistener)

@DOCSTRING(dellistener)

An example of the use of these two functions might be

@example
@group
x = 0:0.1:10;
hg = hggroup ();
h = plot (x, sin (x), "color", [1, 0, 0], "parent", hg);
addproperty ("linestyle", hg, "linelinestyle", get (h, "linestyle"));
addlistener (hg, "linestyle", @@update_props);
hold on
plot (x, cos (x), "color", [0, 1, 0], "parent", hg);

function update_props (h, d)
  set (get (h, "children"), "linestyle", get (h, "linestyle"));
endfunction
@end group
@end example

@noindent
that adds a @code{linestyle} property to the @code{hggroup} and
propagating any changes its value to the children of the group.  The
@code{linkprop} function can be used to simplify the above to be

@example
@group
x = 0:0.1:10;
hg = hggroup ();
h1 = plot (x, sin (x), "color", [1, 0, 0], "parent", hg);
addproperty ("linestyle", hg, "linelinestyle", get (h, "linestyle"));
hold on
h2 = plot (x, cos (x), "color", [0, 1, 0], "parent", hg);
hlink = linkprop ([hg, h1, h2], "color");
@end group
@end example

@DOCSTRING(linkprop)

@DOCSTRING(linkaxes)

These capabilities are used in a number of basic graphics objects.
The @code{hggroup} objects created by the functions of Octave contain
one or more graphics object and are used to:

@itemize @bullet
@item group together multiple graphics objects,

@item create linked properties between different graphics objects, and

@item to hide the nominal user data, from the actual data of the objects.
@end itemize

@noindent
For example the @code{stem} function creates a stem series where each
@code{hggroup} of the stem series contains two line objects representing
the body and head of the stem.  The @code{ydata} property of the
@code{hggroup} of the stem series represents the head of the stem,
whereas the body of the stem is between the baseline and this value.  For
example

@example
@group
h = stem (1:4)
get (h, "xdata")
@result{} [  1   2   3   4]'
get (get (h, "children")(1), "xdata")
@result{} [  1   1 NaN   2   2 NaN   3   3 NaN   4   4 NaN]'
@end group
@end example

@noindent
shows the difference between the @code{xdata} of the @code{hggroup}
of a stem series object and the underlying line.

The basic properties of such group objects is that they consist of one
or more linked @code{hggroup}, and that changes in certain properties of
these groups are propagated to other members of the group.  Whereas,
certain properties of the members of the group only apply to the current
member.

In addition the members of the group can also be linked to other
graphics objects through callback functions.  For example the baseline of
the @code{bar} or @code{stem} functions is a line object, whose length
and position are automatically adjusted, based on changes to the
corresponding hggroup elements.

@menu
* Data Sources in Object Groups::
* Area Series::
* Bar Series::
* Contour Groups::
* Error Bar Series::
* Line Series::
* Quiver Group::
* Scatter Group::
* Stair Group::
* Stem Series::
* Surface Group::
@end menu

@node Data Sources in Object Groups
@subsubsection Data Sources in Object Groups
@cindex data sources in object groups
@anchor{XREFdatasources}
All of the group objects contain data source parameters.  There are
string parameters that contain an expression that is evaluated to update
the relevant data property of the group when the @code{refreshdata}
function is called.

@DOCSTRING(refreshdata)

@anchor{XREFlinkdata}
@c add the description of the linkdata function here when it is written
@c remove the explicit anchor when you add the corresponding @DOCSTRING
@c command

@node Area Series
@subsubsection Area Series
@cindex series objects
@cindex area series

Area series objects are created by the @code{area} function.  Each of the
@code{hggroup} elements contains a single patch object.  The properties
of the area series are

@table @code
@item basevalue
The value where the base of the area plot is drawn.

@item  linewidth
@itemx linestyle
The line width and style of the edge of the patch objects making up the
areas.  @xref{Line Styles}.

@item  edgecolor
@itemx facecolor
The line and fill color of the patch objects making up the areas.
@xref{Colors}.

@item  xdata
@itemx ydata
The x and y coordinates of the original columns of the data passed to
@code{area} prior to the cumulative summation used in the @code{area}
function.

@item  xdatasource
@itemx ydatasource
Data source variables.
@end table

@node Bar Series
@subsubsection Bar Series
@cindex series objects
@cindex bar series

Bar series objects are created by the @code{bar} or @code{barh}
functions.  Each @code{hggroup} element contains a single patch object.
The properties of the bar series are

@table @code
@item  showbaseline
@itemx baseline
@itemx basevalue
The property @code{showbaseline} flags whether the baseline of the bar
series is displayed (default is @qcode{"on"}).  The handle of the graphics
object representing the baseline is given by the @code{baseline} property and
the y-value of the baseline by the @code{basevalue} property.

Changes to any of these properties are propagated to the other members of
the bar series and to the baseline itself.  Equally, changes in the
properties of the base line itself are propagated to the members of the
corresponding bar series.

@item  barwidth
@itemx barlayout
@itemx horizontal
The property @code{barwidth} is the width of the bar corresponding to
the @var{width} variable passed to @code{bar} or @var{barh}.  Whether the
bar series is @qcode{"grouped"} or @qcode{"stacked"} is determined by the
@code{barlayout} property and whether the bars are horizontal or
vertical by the @code{horizontal} property.

Changes to any of these property are propagated to the other members of
the bar series.

@item  linewidth
@itemx linestyle
The line width and style of the edge of the patch objects making up the
bars.  @xref{Line Styles}.

@item  edgecolor
@itemx facecolor
The line and fill color of the patch objects making up the bars.  @xref{Colors}.

@item xdata
The nominal x positions of the bars.  Changes in this property and
propagated to the other members of the bar series.

@item ydata
The y value of the bars in the @code{hggroup}.

@item  xdatasource
@itemx ydatasource
Data source variables.
@end table

@node Contour Groups
@subsubsection Contour Groups
@cindex series objects
@cindex contour series

Contour group objects are created by the @code{contour}, @code{contourf}
and @code{contour3} functions.  The are equally one of the handles returned
by the @code{surfc} and @code{meshc} functions.  The properties of the contour
group are

@table @code
@item contourmatrix
A read only property that contains the data return by @code{contourc} used to
create the contours of the plot.

@item fill
A radio property that can have the values @qcode{"on"} or @qcode{"off"} that
flags whether the contours to plot are to be filled.

@item  zlevelmode
@itemx zlevel
The radio property @code{zlevelmode} can have the values @qcode{"none"},
@qcode{"auto"}, or @qcode{"manual"}.  When its value is @qcode{"none"} there is
no z component to the plotted contours.  When its value is @qcode{"auto"} the z
value of the plotted contours is at the same value as the contour itself.  If
the value is @qcode{"manual"}, then the z value at which to plot the contour is
determined by the @code{zlevel} property.

@item  levellistmode
@itemx levellist
@itemx levelstepmode
@itemx levelstep
If @code{levellistmode} is @qcode{"manual"}, then the levels at which to plot
the contours is determined by @code{levellist}.  If @code{levellistmode} is set
to @qcode{"auto"}, then the distance between contours is determined by
@code{levelstep}.  If both @code{levellistmode} and @code{levelstepmode} are
set to @qcode{"auto"}, then there are assumed to be 10 equal spaced contours.

@item  textlistmode
@itemx textlist
@itemx textstepmode
@itemx textstep
If @code{textlistmode} is @qcode{"manual"}, then the labeled contours
is determined by @code{textlist}.  If @code{textlistmode} is set to
@qcode{"auto"}, then the distance between labeled contours is determined by
@code{textstep}.  If both @code{textlistmode} and @code{textstepmode}
are set to @qcode{"auto"}, then there are assumed to be 10 equal spaced
labeled contours.

@item showtext
Flag whether the contour labels are shown or not.

@item labelspacing
The distance between labels on a single contour in points.

@item linewidth

@item linestyle

@item linecolor
The properties of the contour lines.  The properties @code{linewidth} and
@code{linestyle} are similar to the corresponding properties for lines.  The
property @code{linecolor} is a color property (@pxref{Colors}), that can also
have the values of @qcode{"none"} or @qcode{"auto"}.  If @code{linecolor} is
@qcode{"none"}, then no contour line is drawn.  If @code{linecolor} is
@qcode{"auto"} then the line color is determined by the colormap.

@item  xdata
@itemx ydata
@itemx zdata
The original x, y, and z data of the contour lines.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
Data source variables.
@end table

@node Error Bar Series
@subsubsection Error Bar Series
@cindex series objects
@cindex error bar series

Error bar series are created by the @code{errorbar} function.  Each
@code{hggroup} element contains two line objects representing the data and
the errorbars separately.  The properties of the error bar series are

@table @code
@item color
The RGB color or color name of the line objects of the error bars.
@xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the line objects of the error bars.  @xref{Line
Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
@itemx markersize
The line and fill color of the markers on the error bars.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx ldata
@itemx udata
@itemx xldata
@itemx xudata
The original x, y, l, u, xl, xu data of the error bars.

@item  xdatasource
@itemx ydatasource
@itemx ldatasource
@itemx udatasource
@itemx xldatasource
@itemx xudatasource
Data source variables.
@end table

@node Line Series
@subsubsection Line Series
@cindex series objects
@cindex line series

Line series objects are created by the @code{plot}  and @code{plot3}
functions and are of the type @code{line}.  The properties of the
line series with the ability to add data sources.

@table @code
@item color
The RGB color or color name of the line objects.  @xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the line objects.  @xref{Line Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
@itemx markersize
The line and fill color of the markers.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx zdata
The original x, y and z data.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
Data source variables.
@end table

@node Quiver Group
@subsubsection Quiver Group
@cindex group objects
@cindex quiver group

Quiver series objects are created by the @code{quiver} or @code{quiver3}
functions.  Each @code{hggroup} element of the series contains three line
objects as children representing the body and head of the arrow,
together with a marker as the point of origin of the arrows.  The
properties of the quiver series are

@table @code
@item  autoscale
@itemx autoscalefactor
Flag whether the length of the arrows is scaled or defined directly from
the @var{u}, @var{v} and @var{w} data.  If the arrow length is flagged
as being scaled by the @code{autoscale} property, then the length of the
autoscaled arrow is controlled by the @code{autoscalefactor}.

@item maxheadsize
This property controls the size of the head of the arrows in the quiver
series.  The default value is 0.2.

@item showarrowhead
Flag whether the arrow heads are displayed in the quiver plot.

@item color
The RGB color or color name of the line objects of the quiver.  @xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the line objects of the quiver.  @xref{Line Styles}.

@item  marker
@itemx markerfacecolor
@itemx markersize
The line and fill color of the marker objects at the original of the
arrows.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx zdata
The origins of the values of the vector field.

@item  udata
@itemx vdata
@itemx wdata
The values of the vector field to plot.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
@itemx udatasource
@itemx vdatasource
@itemx wdatasource
Data source variables.
@end table

@node Scatter Group
@subsubsection Scatter Group
@cindex group objects
@cindex scatter group

Scatter series objects are created by the @code{scatter} or @code{scatter3}
functions.  A single hggroup element contains as many children as there are
points in the scatter plot, with each child representing one of the points.
The properties of the stem series are

@table @code
@item linewidth
The line width of the line objects of the points.  @xref{Line Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
The line and fill color of the markers of the points.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx zdata
The original x, y and z data of the stems.

@item cdata
The color data for the points of the plot.  Each point can have a separate
color, or a unique color can be specified.

@item sizedata
The size data for the points of the plot.  Each point can its own size or a
unique size can be specified.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
@itemx cdatasource
@itemx sizedatasource
Data source variables.
@end table

@node Stair Group
@subsubsection Stair Group
@cindex group objects
@cindex stair group

Stair series objects are created by the @code{stair} function.  Each
@code{hggroup} element of the series contains a single line object as a
child representing the stair.  The properties of the stair series are

@table @code
@item color
The RGB color or color name of the line objects of the stairs.  @xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the line objects of the stairs.  @xref{Line Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
@itemx markersize
The line and fill color of the markers on the stairs.  @xref{Colors}.

@item  xdata
@itemx ydata
The original x and y data of the stairs.

@item  xdatasource
@itemx ydatasource
Data source variables.
@end table

@node Stem Series
@subsubsection Stem Series
@cindex series objects
@cindex stem series

Stem series objects are created by the @code{stem} or @code{stem3}
functions.  Each @code{hggroup} element contains a single line object
as a child representing the stems.  The properties of the stem series
are

@table @code
@item  showbaseline
@itemx baseline
@itemx basevalue
The property @code{showbaseline} flags whether the baseline of the
stem series is displayed (default is @qcode{"on"}).  The handle of the graphics
object representing the baseline is given by the @code{baseline}
property and the y-value (or z-value for @code{stem3}) of the baseline
by the @code{basevalue} property.

Changes to any of these property are propagated to the other members of
the stem series and to the baseline itself.  Equally changes in the
properties of the base line itself are propagated to the members of the
corresponding stem series.

@item color
The RGB color or color name of the line objects of the stems.  @xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the line objects of the stems.  @xref{Line Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
@itemx markersize
The line and fill color of the markers on the stems.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx zdata
The original x, y and z data of the stems.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
Data source variables.
@end table

@node Surface Group
@subsubsection Surface Group
@cindex group objects
@cindex surface group

Surface group objects are created by the @code{surf} or @code{mesh}
functions, but are equally one of the handles returned by the @code{surfc}
or @code{meshc} functions.  The surface group is of the type @code{surface}.

The properties of the surface group are

@table @code
@item edgecolor

@item facecolor
The RGB color or color name of the edges or faces of the surface.
@xref{Colors}.

@item  linewidth
@itemx linestyle
The line width and style of the lines on the surface.  @xref{Line Styles}.

@item  marker
@itemx markeredgecolor
@itemx markerfacecolor
@itemx markersize
The line and fill color of the markers on the surface.  @xref{Colors}.

@item  xdata
@itemx ydata
@itemx zdata
@itemx cdata
The original x, y, z and c data.

@item  xdatasource
@itemx ydatasource
@itemx zdatasource
@itemx cdatasource
Data source variables.
@end table

@node Graphics Toolkits
@subsection Graphics Toolkits
@cindex graphics toolkits
@cindex toolkits, graphics

@DOCSTRING(graphics_toolkit)

@DOCSTRING(available_graphics_toolkits)

@DOCSTRING(loaded_graphics_toolkits)

@DOCSTRING(register_graphics_toolkit)

@menu
* Customizing Toolkit Behavior::
@end menu

@node Customizing Toolkit Behavior
@subsubsection Customizing Toolkit Behavior
@cindex toolkit customization

The specific behavior of the backend toolkit may be modified using the
following utility functions.  Note: Not all functions apply to every
graphics toolkit.

@DOCSTRING(gnuplot_binary)