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  <title>Interpolating data (LTPDA Toolbox)</title>
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  <h1 class="title"><a name="f3-12899" id="f3-12899"></a>Interpolating data</h1>
  <hr>

  <p>
	<h2>Description</h2>
<p>
  Interpolation of data can be done in the LTPDA Toolbox by means of
  <a href="matlab:doc('ao/interp')"><tt>interp</tt></a>.
  This function interpolates the values in the input AO(s) at new values specified by the
  input parameter list.
</p>
<p>
  <a href="matlab:doc('ao/interp')"><tt>Interp</tt></a> overloads <tt>interp1</tt> function of
  Matlab Signal Processing Toolbox for AOs.
</p>
<br>
<br>
<h2>Syntax</h2>
</p>
<div class="fragment"><pre>
    <br>
    b = interpolate(a, pl)
  </pre>
</div>
<h2>Parameters</h2>
<p>
  The following parameters can be set in the method:
  <ul>
    <li> <tt>vertices</tt> - specify the new vertices to interpolate on </li>
    <li> <tt>method</tt> - four methods are available for interpolating data</li>
    <ul>
      <li> 'nearest'- nearest neighbor interpolation </li>
      <li> 'linear' - linear interpolation </li>
      <li> 'spline' - spline interpolation (default option) 	</li>
      <li> 'cubic' - shape-preserving piecewise cubic interpolation </li>
    </ul>
  </ul>
  For details see <tt>interp1</tt> help of Matlab.
</p>
<p>
  <h2>Examples</h2>
</p>
<p>
  1. Interpolation of a sequence of random data at original sampling rate of 1 Hz
  by a factor of 10 with no initial phase.
</p>
<div class="fragment"><pre>
    <br>
    <span class="comment">% Signal generation</span>
    pl = plist(<span class="string">'tsfcn'</span>,<span class="string">'sin(2*pi*1.733*t)'</span>,...
    <span class="string">'fs'</span>,1,<span class="string">'nsecs'</span>,10,...
    <span class="string">'yunits'</span>,<span class="string">'V'</span>);
    x = ao(pl);
    <span class="comment">% Interpolate on a new time vector</span>
    t = linspace(0, x.data.nsecs - 1/x.data.fs, 2*len(x));
    pl_spline  = plist(<span class="string">'vertices'</span>,t);
    pl_nearest = plist(<span class="string">'vertices'</span>,t,<span class="string">'method'</span>,<span class="string">'nearest'</span>);
    x_spline   = interp(x,pl_spline);
    x_nearest  = interp(x,pl_nearest);
    iplot([x x_spline x_nearest], plist(<span class="string">'Markers'</span>, {<span class="string">'x'</span>, <span class="string">'o'</span>, <span class="string">'+'</span>}, ...
    <span class="string">'LineColors'</span>, {<span class="string">'k'</span>, <span class="string">'r'</span>}));
  </pre>
</div>
<br>
<br>
<img src="images/interp.png" alt="Interpolate" border="0">

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  <p class="copy">&copy;LTP Team</p>
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author	Daniele Nicolodi <nicolodi@science.unitn.it>
date	Wed, 23 Nov 2011 19:22:13 +0100
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