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<div class="subsection-level-extent" id="Introduction-to-Graphics-Structures">
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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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<h4 class="subsection" id="Introduction-to-Graphics-Structures-1"><span>15.3.1 Introduction to Graphics Structures<a class="copiable-link" href="#Introduction-to-Graphics-Structures-1"> ¶</a></span></h4>
<a class="index-entry-id" id="index-introduction-to-graphics-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. These objects are the graphics data structures themselves. The
primitive graphic object types are: <code class="code">figure</code>, <code class="code">axes</code>, <code class="code">line</code>,
<code class="code">text</code>, <code class="code">patch</code>, <code class="code">scatter</code>, <code class="code">surface</code>, <code class="code">text</code>,
<code class="code">image</code>, and <code class="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 class="code">plot</code> and <code class="code">plot3</code>
return a handle pointing to an object of type <code class="code">line</code>. The function
<code class="code">subplot</code> returns a handle pointing to an object of type <code class="code">axes</code>.
The functions <code class="code">fill</code>, <code class="code">fill3</code>, <code class="code">trimesh</code>, and <code class="code">trisurf</code>
return a handle pointing to an object of type patch. The function
<code class="code">scatter3</code> returns a handle to an object of type scatter. The functions
<code class="code">slice</code>, <code class="code">surf</code>, <code class="code">surfl</code>, <code class="code">mesh</code>, <code class="code">meshz</code>,
<code class="code">pcolor</code>, and <code class="code">waterfall</code> each return a handle of type surface. The
function <code class="code">camlight</code> returns a handle to an object of type light. The
functions <code class="code">area</code>, <code class="code">bar</code>, <code class="code">barh</code>, <code class="code">contour</code>,
<code class="code">contourf</code>, <code class="code">contour3</code>, <code class="code">surfc</code>, <code class="code">meshc</code>, <code class="code">errorbar</code>,
<code class="code">quiver</code>, <code class="code">quiver3</code>, <code class="code">stair</code>, <code class="code">stem</code>, <code class="code">stem3</code> each
return a handle to a complex data structure as documented in
<a class="ref" href="Data-Sources-in-Object-Groups.html">Data Sources</a>.
</p>
<p>The graphics objects are arranged in a hierarchy:
</p>
<p>1. The root object is returned by <code class="code">groot</code> (historically, equivalent to
the handle 0). In other words, <code class="code">get (groot)</code> returns the properties of
the root object.
</p>
<p>2. Below the root are <code class="code">figure</code> objects.
</p>
<p>3. Below the <code class="code">figure</code> objects are <code class="code">axes</code> or <code class="code">hggroup</code> objects.
</p>
<p>4. Below the <code class="code">axes</code> or <code class="code">hggroup</code> objects are <code class="code">line</code>,
<code class="code">text</code>, <code class="code">patch</code>, <code class="code">scatter</code>, <code class="code">surface</code>, <code class="code">image</code>, and
<code class="code">light</code> objects.
</p>
<p>It is possible to walk this hierarchical tree by querying the <code class="code">"parent"</code>
and <code class="code">"children"</code> properties of the graphics objects.
</p>
<p>Graphics handles may be distinguished from function handles
(see <a class="pxref" href="Function-Handles.html">Function Handles</a>) by means of the function <code class="code">ishghandle</code>.
<code class="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 class="code">isfigure</code> or <code class="code">isaxes</code> respectively. To test for a specific type of
graphics handle, such as a patch or line object, use <code class="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 class="code">get</code> and <code class="code">set</code> commands are used to obtain and set the values of
properties of graphics objects. In addition, the <code class="code">get</code> command may be
used to obtain property names.
</p>
<p>For example, the property <code class="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-preformatted">get (h, "type")
</pre></div>
<p>The properties and their current values may be obtained in the form of a
structure using <code class="code">s = get (h)</code>, where <code class="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 class="code">set (h)</code>.
</p>
<p>Thus, for example:
</p>
<div class="example">
<pre class="example-preformatted">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 class="code">get</code> and <code class="code">set</code> are further explained in
<a class="ref" href="Handle-Functions.html#XREFget">get</a>, <a class="ref" href="Handle-Functions.html#XREFset">set</a>.
</p>
<a class="anchor" id="XREFisprop"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-isprop"><span><code class="def-type"><var class="var">res</var> =</code> <strong class="def-name">isprop</strong> <code class="def-code-arguments">(<var class="var">obj</var>, "<var class="var">prop</var>")</code><a class="copiable-link" href="#index-isprop"> ¶</a></span></dt>
<dd><p>Return true if <var class="var">prop</var> is a property of the object <var class="var">obj</var>.
</p>
<p><var class="var">obj</var> may also be an array of objects in which case <var class="var">res</var> will be a
logical array indicating whether each handle has the property <var class="var">prop</var>.
</p>
<p>For plotting, <var class="var">obj</var> is a handle to a graphics object. Otherwise,
<var class="var">obj</var> should be an instance of a class. <code class="code">isprop</code> reports whether
the class defines a property, but <code class="code">Access</code> permissions or visibility
restrictions (<code class="code">Hidden = true</code>) may prevent use by the programmer.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Handle-Functions.html#XREFget">get</a>, <a class="ref" href="Handle-Functions.html#XREFset">set</a>, <a class="ref" href="Properties.html#XREFproperties">properties</a>, <a class="ref" href="Creating-a-Class.html#XREFismethod">ismethod</a>, <a class="ref" href="Creating-a-Class.html#XREFisobject">isobject</a>.
</p></dd></dl>
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