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Daniele Nicolodi <nicolodi@science.unitn.it> |
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Mon, 05 Dec 2011 16:20:06 +0100 (2011-12-05) |
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<h1 class="title"><a name="f3-12899" id="f3-12899"></a>Resampling data</h1>
<hr>
<p>
<h2>Description</h2>
<p>
Resampling is the process of changing the sampling rate of data. <a href="matlab:doc('ao/resample')"><tt>Resample</tt></a>
changes the sampling rate of the input AOs to the desired output sampling frequency. LTPDA <a href="matlab:doc('ao/resample')"><tt>resample</tt></a> overloads <tt>resample</tt> function of Matlab Signal Processing Toolbox for AOs.
</p>
<h2>Syntax</h2>
<div class="fragment"><pre>
<br>
b = resample(a, pl)
</pre>
</div>
<h2>Parameters</h2>
<p> The following parameters can be set:
<ul>
<li> <tt>fsout</tt> - specify the desired output frequency (must be positive and integer)</li>
<li> <tt>filter</tt> - specified filter applied to the input, <tt>a</tt>, in the resampling process</li>
</ul>
</p>
<p>
<h2>Examples</h2>
</p>
<p>
2. Resampling a sequence of random data at original sampling rate of 1 Hz at an output sampling of 50 Hz.
</p>
<div class="fragment"><pre>
<br>
<span class="comment">% create an AO of random data with fs = 10 Hz</span>
pl = plist(<span class="string">'tsfcn'</span>, <span class="string">'randn(size(t))'</span>,<span class="string">'fs'</span>,1,<span class="string">'nsecs'</span>,10,<span class="string">'yunits'</span>,<span class="string">'m'</span>,<span class="string">'nsecs'</span>,100);
x = ao(pl);
y = resample(x, plist(<span class="string">'fsout'</span>, 50)); <span class="comment">% resample the input AO (x) to obtain the resampled output AO (y)</span>
iplot(x, y) <span class="comment">% plot original and resampled data</span>
</pre>
</div>
<br>
<br>
<img src="images/resample1.png" alt="Resample">
<br>
<br>
<br>
<p>
1. Resampling a sequence of random data at original sampling rate of 10 Hz at an output sampling of 1 Hz with
a filter defined by the user.
</p>
<div class="fragment"><pre>
<br>
<span class="comment">% create an AO of random data with fs = 10 Hz</span>
pl = plist(<span class="string">'tsfcn'</span>, <span class="string">'randn(size(t))'</span>,<span class="string">'fs'</span>,10,<span class="string">'nsecs'</span>,10,<span class="string">'yunits'</span>,<span class="string">'m'</span>);
x = ao(pl)
<span class="comment">% filter definition</span>
plfilter = plist(<span class="string">'type'</span>,<span class="string">'lowpass'</span>,<span class="string">'Win'</span>,specwin(<span class="string">'Kaiser'</span>, 10, 150),<span class="string">'order'</span>,32,<span class="string">'fs'</span>,10,<span class="string">'fc'</span>,1);
f = mfir(plfilter)
<span class="comment">% resampling</span>
pl = plist(<span class="string">'fsout'</span>, 1, <span class="string">'filter'</span>,f); <span class="comment">% define parameters list with fsout = 1 Hz and the defined filter</span>
y = resample(x, pl); <span class="comment">% resample the input AO (x) to obtain the resampled output AO (y)</span>
iplot(x, y) <span class="comment">% plot original and resampled data</span>
</pre>
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<br>
<br>
<img src="images/resample2.png" alt="Resample" border="0">
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