<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>