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<div class="subsection" id="Introduction-to-Graphics-Structures">
<div class="header">
<p>
Next: <a href="Graphics-Objects.html" accesskey="n" rel="next">Graphics Objects</a>, Up: <a href="Graphics-Data-Structures.html" accesskey="u" rel="up">Graphics Data Structures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Introduction-to-Graphics-Structures-1"></span><h4 class="subsection">15.3.1 Introduction to Graphics Structures</h4>
<span id="index-introduction-to-graphics-structures"></span>
<span id="XREFgraphics-structures"></span>
<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. 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>scatter</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.
</p>
<p>In addition, there are several functions which operate on properties of the
graphics objects and which also return handles. This includes but is not
limited to the following functions: The functions <code>plot</code> and <code>plot3</code>
return a handle pointing to an object of type <code>line</code>. The function
<code>subplot</code> returns a handle pointing to an object of type <code>axes</code>.
The functions <code>fill</code>, <code>fill3</code>, <code>trimesh</code>, and <code>trisurf</code>
return a handle pointing to an object of type patch. The function
<code>scatter3</code> returns a handle to an object of type scatter. The functions
<code>slice</code>, <code>surf</code>, <code>surfl</code>, <code>mesh</code>, <code>meshz</code>,
<code>pcolor</code>, and <code>waterfall</code> each return a handle of type surface. The
function <code>camlight</code> returns a handle to an object of type light. The
functions <code>area</code>, <code>bar</code>, <code>barh</code>, <code>contour</code>,
<code>contourf</code>, <code>contour3</code>, <code>surfc</code>, <code>meshc</code>, <code>errorbar</code>,
<code>quiver</code>, <code>quiver3</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> or <code>hggroup</code> objects are <code>line</code>,
<code>text</code>, <code>patch</code>, <code>scatter</code>, <code>surface</code>, <code>image</code>, and
<code>light</code> objects.
</p>
<p>It is possible to walk this hierarchical tree by querying the <code>"parent"</code>
and <code>"children"</code> properties of the graphics objects.
</p>
<p>Graphics handles may be distinguished from function handles
(see <a href="Function-Handles.html">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>"type"</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, "type")
</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, "type")
⇒ ans = figure
set (h)
⇒
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>
<span id="XREFisprop"></span><dl class="def">
<dt id="index-isprop"><span class="category">: </span><span><em><var>res</var> =</em> <strong>isprop</strong> <em>(<var>obj</var>, "<var>prop</var>")</em><a href='#index-isprop' class='copiable-anchor'> ¶</a></span></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. <code>isprop</code> reports whether
the class defines a property, but <code>Access</code> permissions or visibility
restrictions (<code>Hidden = true</code>) may prevent use by the programmer.
</p>
<p><strong>See also:</strong> <a href="Graphics-Objects.html#XREFget">get</a>, <a href="Graphics-Objects.html#XREFset">set</a>, <a href="Properties.html#XREFproperties">properties</a>, <a href="Creating-a-Class.html#XREFismethod">ismethod</a>, <a href="Creating-a-Class.html#XREFisobject">isobject</a>.
</p></dd></dl>
</div>
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Next: <a href="Graphics-Objects.html">Graphics Objects</a>, Up: <a href="Graphics-Data-Structures.html">Graphics Data Structures</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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