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<a name="Introduction-to-Graphics-Structures"></a>
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<p>
Next: <a href="Graphics-Objects.html#Graphics-Objects" accesskey="n" rel="next">Graphics Objects</a>, Up: <a href="Graphics-Data-Structures.html#Graphics-Data-Structures" accesskey="u" rel="up">Graphics Data Structures</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="Introduction-to-Graphics-Structures-1"></a>
<h4 class="subsection">15.3.1 Introduction to Graphics Structures</h4>
<a name="index-introduction-to-graphics-structures"></a>
<a name="XREFgraphics-structures"></a>
<p>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>, <code>axes</code>, <code>line</code>,
<code>text</code>, <code>patch</code>, <code>surface</code>, <code>text</code>, <code>image</code>, and
<code>light</code>.
</p>
<p>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</code>
and <code>plot3</code> return a handle pointing to an object of type line, the
function <code>subplot</code> returns a handle pointing to an object of type axes,
the function <code>fill</code> returns a handle pointing to an object of type patch,
the functions <code>area</code>, <code>bar</code>, <code>barh</code>, <code>contour</code>,
<code>contourf</code>, <code>contour3</code>, <code>surf</code>, <code>mesh</code>, <code>surfc</code>,
<code>meshc</code>, <code>errorbar</code>, <code>quiver</code>, <code>quiver3</code>, <code>scatter</code>,
<code>scatter3</code>, <code>stair</code>, <code>stem</code>, <code>stem3</code> each return a handle
to a complex data structure as documented in
<a href="Data-Sources-in-Object-Groups.html#XREFdatasources">Data Sources</a>.
</p>
<p>The graphics objects are arranged in a hierarchy:
</p>
<p>1. The root object is returned by <code>groot</code> (historically, equivalent to
the handle 0).  In other words, <code>get (groot)</code> returns the properties of
the root object.
</p>
<p>2. Below the root are <code>figure</code> objects.
</p>
<p>3. Below the <code>figure</code> objects are <code>axes</code> or <code>hggroup</code> objects.
</p>
<p>4. Below the <code>axes</code> objects are <code>line</code>, <code>text</code>, <code>patch</code>,
<code>surface</code>, <code>image</code>, and <code>light</code> objects.
</p>
<p>Graphics handles may be distinguished from function handles
(see <a href="Function-Handles.html#Function-Handles">Function Handles</a>) by means of the function <code>ishghandle</code>.
<code>ishghandle</code> 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</code> or <code>isaxes</code> respectively.  To test for a specific type of
graphics handle, such as a patch or line object, use <code>isgraphics</code>.  The
more specific test functions return true only if the argument is both a
graphics handle and of the correct type (figure, axes, specified object type).
</p>
<p>The <code>get</code> and <code>set</code> commands are used to obtain and set the values of
properties of graphics objects.  In addition, the <code>get</code> command may be
used to obtain property names.
</p>
<p>For example, the property <code>&quot;type&quot;</code> of the graphics object pointed to by
the graphics handle h may be displayed by:
</p>
<div class="example">
<pre class="example">get (h, &quot;type&quot;)
</pre></div>

<p>The properties and their current values may be obtained in the form of a
structure using <code>s = get (h)</code>, where <code>h</code> is the handle of a graphics
object.  If only the names of the properties and the allowed values (for radio
properties only) are wanted, one may use <code>set (h)</code>.
</p>
<p>Thus, for example:
</p>
<div class="example">
<pre class="example">h = figure ();
get (h, &quot;type&quot;)
&rArr; ans = figure
set (h)
&rArr;
        alphamap:
        beingdeleted:  [ {off} | on ]
        busyaction:  [ cancel | {queue} ]
        buttondownfcn:
        clipping:  [ off | {on} ]
        closerequestfcn:
        color:
        colormap:
        createfcn:
        currentaxes:
        deletefcn:
        dockcontrols:  [ {off} | on ]
        filename:
        graphicssmoothing:  [ off | {on} ]
        handlevisibility:  [ callback | off | {on} ]
        ...
</pre></div>

<p>The uses of <code>get</code> and <code>set</code> are further explained in
<a href="Graphics-Objects.html#XREFget">get</a>, <a href="Graphics-Objects.html#XREFset">set</a>.
</p>
<a name="XREFisprop"></a><dl>
<dt><a name="index-isprop"></a><em><var>res</var> =</em> <strong>isprop</strong> <em>(<var>obj</var>, &quot;<var>prop</var>&quot;)</em></dt>
<dd><p>Return true if <var>prop</var> is a property of the object <var>obj</var>.
</p>
<p><var>obj</var> may also be an array of objects in which case <var>res</var> will be a
logical array indicating whether each handle has the property <var>prop</var>.
</p>
<p>For plotting, <var>obj</var> is a handle to a graphics object.  Otherwise,
<var>obj</var> should be an instance of a class.
</p>
<p><strong>See also:</strong> <a href="Graphics-Objects.html#XREFget">get</a>, <a href="Graphics-Objects.html#XREFset">set</a>, <a href="Creating-a-Class.html#XREFismethod">ismethod</a>, <a href="Creating-a-Class.html#XREFisobject">isobject</a>.
</p></dd></dl>


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Next: <a href="Graphics-Objects.html#Graphics-Objects" accesskey="n" rel="next">Graphics Objects</a>, Up: <a href="Graphics-Data-Structures.html#Graphics-Data-Structures" accesskey="u" rel="up">Graphics Data Structures</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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