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<h1 class="title"><a name="f3-12899" id="f3-12899"></a>Working with LTPDA objects</h1>
<hr>
<p>
<p>
The use of LTPDA objects requires some understanding of the nature of objects as implemented in MATLAB.
</p>
<p>
For full details of objects in MATLAB, refer to <a href="matlab:web(['jar:file:///' matlabroot '/help/techdoc/help.jar!/matlab_oop/ug_intropage.html'])">MATLAB Classes and Object-Oriented Programming</a>.
For convenience, the most important aspects in the context of LTPDA are reviewed below.
</p>
<p>
<ul>
<li>
<p><a href="objects_working.html#calling">Calling object methods</a></p>
</li>
<li>
<p><a href="objects_working.html#set">Setting object properties</a></p>
</li>
<li>
<p><a href="objects_working.html#copy">Copying objects</a></p>
</li>
<li><a href="objects_working.html#exploring">Exploring objects</a></li>
</ul>
</p>
<a name="calling" id= "calling"><h3 class="title">Calling object methods</h3></a>
<p>
Each class in LTPDA has a set of methods (functions) which can operate/act on instances of the class (objects).
For example, the AO class has a method <tt>psd</tt> which can compute the Power Spectral Density estimate of a
time-series AO.
</p>
<p>
To see which methods a particular class has, use the <tt>methods</tt> command. For example,
<div class="fragment"><pre>
>> methods(<span class="string">'ao'</span>)
</pre></div>
</p>
<p>
To call a method on an object, <tt>obj.method</tt>, or, <tt>method(obj)</tt>. For example,
<div class="fragment"><pre>
>> b = a.psd
</pre></div>
or
<div class="fragment"><pre>
>> b = psd(a)
</pre></div>
Additional arguments can be passed to the method (a <tt>plist</tt>, for example), as follows:
<div class="fragment"><pre>
>> b = a.psd(pl)
</pre></div>
or
<div class="fragment"><pre>
>> b = psd(a, pl)
</pre></div>
</p><br>
<p>
In order to pass multiple objects to a method, you must use the form
<div class="fragment"><pre>
>> b = psd(a1, a2, pl)
</pre></div>
</p><br>
<p>
Some methods can behave as modifiers which means that the object which the method acts on is modified. To
modify an object, just give no output. If we start with a time-series AO then modify it with the <tt>psd</tt>
method,
<div class="fragment"><pre>
>> a = ao(1:100, randn(100,1), 10)
>> a
M: running ao/display
----------- ao 01: a -----------
name: None
data: (0,0.840375529753905) (0.1,-0.88803208232901) (0.2,0.100092833139322) (0.3,-0.544528929990548) (0.4,0.303520794649354) ...
-------- tsdata 01 ------------
fs: 10
x: [100 1], double
y: [100 1], double
dx: [0 0], double
dy: [0 0], double
xunits: [s]
yunits: []
nsecs: 10
t0: 1970-01-01 00:00:01.000
-------------------------------
hist: ao / ao / SId: fromVals ... -->$Id: ao .... S
mdlfile: empty
description:
UUID: 8cffab46-61f0-494a-af03-eb310aa76114
--------------------------------
</pre></div><br>
Then call the <tt>psd</tt> method:
<div class="fragment"><pre>
>> a.psd
M: running ao/psd
M: running ao/len
M: running ao/len
M: running ao/display
----------- ao 01: PSD(a) -----------
name: PSD(a)
data: (0,0.117412356146407) (0.1,0.179893990497347) (0.2,0.173957816470448) (0.3,0.245076068355785) (0.4,0.213036543621994) ...
----------- fsdata 01 -----------
fs: 10
x: [51 1], double
y: [51 1], double
dx: [0 0], double
dy: [0 0], double
xunits: [Hz]
yunits: [Hz^(-1)]
t0: 1970-01-01 00:00:01.000
navs: 1
---------------------------------
hist: ao / psd / SId: psd.m,v 1.52 2009/09/05 05:57:32 mauro Exp S
mdlfile: empty
description:
UUID: 0d2395cd-22af-4645-a94c-69fa32c15982
-------------------------------------
</pre></div><br>
then the object <tt>a</tt> is converted to a frequency-series AO.
</p><br>
<p>
This modifier behaviour only works with certain methods, in particular, methods requiring more than one input object
will not behave as modifiers.
</p><br>
<a name="set" id= "set"><h3 class="title">Setting object properties</h3></a>
<p>
All object properties must be set using the appropriate setter method. For example, to set the name of a IIR filter
object,
<div class="fragment"><pre>
>> ii = miir();
>> ii.setName(<span class="string">'My Filter'</span>);
</pre></div>
</p>
<p>
Reading the value of a property is achieved by:
<div class="fragment"><pre>
>> ii.name
ans =
My Filter
</pre></div>
</p><br>
<a name="copy" id= "copy"><h3 class="title">Copying objects</h3></a>
<br>
<p>
Since all objects in LTPDA are handle objects, creating copies of objects needs to be done differently than in standard
MATLAB. For example,
<div class="fragment"><pre>
>> a = ao();
>> b = a;
</pre></div>
in this case, the variable <tt>b</tt> is a copy of the handle <tt>a</tt>, not a copy of the object pointed too
by the handle <tt>a</tt>. To see how this behaves,
<div class="fragment"><pre>
>> a = ao();
>> b = a;
>> b.setName(<span class="string">'My Name'</span>);
>> a.name
ans =
My Name
</pre></div>
</p>
<p>
Copying the object can be achieved using the copy constructor:
<div class="fragment"><pre>
>> a = ao();
>> b = ao(a);
>> b.setName(<span class="string">'My Name'</span>);
>> a.name
ans =
none
</pre></div>
<p>In this case, the variable <tt>b</tt> points to a new distinct copy of the object pointed to by <tt>a</tt>.
</p>
</p>
<p></p>
<h3 class="title"><a name="exploring" id="calling2">Exploring objects</a></h3>
<p> A browsing tool is provided on purpose to enable LTPDA objects exploring.</p>
<p><a href="gui_explorer.html">See the LTPDA Objects Explorer GUI documentation.</a></p>
</p>
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