Mercurial > hg > ltpda

diff m-toolbox/html_help/help/ug/downsample.html @ 0:f0afece42f48

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Import.
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Wed, 23 Nov 2011 19:22:13 +0100
parents
children
line wrap: on
line diff
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/m-toolbox/html_help/help/ug/downsample.html	Wed Nov 23 19:22:13 2011 +0100
@@ -0,0 +1,120 @@
+<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
+   "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
+
+<html lang="en">
+<head>
+  <meta name="generator" content=
+  "HTML Tidy for Mac OS X (vers 1st December 2004), see www.w3.org">
+  <meta http-equiv="Content-Type" content=
+  "text/html; charset=us-ascii">
+
+  <title>Downsampling data (LTPDA Toolbox)</title>
+  <link rel="stylesheet" href="docstyle.css" type="text/css">
+  <meta name="generator" content="DocBook XSL Stylesheets V1.52.2">
+  <meta name="description" content=
+  "Presents an overview of the features, system requirements, and starting the toolbox.">
+  </head>
+
+<body>
+  <a name="top_of_page" id="top_of_page"></a>
+
+  <p style="font-size:1px;">&nbsp;</p>
+
+  <table class="nav" summary="Navigation aid" border="0" width=
+  "100%" cellpadding="0" cellspacing="0">
+    <tr>
+      <td valign="baseline"><b>LTPDA Toolbox</b></td><td><a href="../helptoc.html">contents</a></td>
+
+      <td valign="baseline" align="right"><a href=
+      "preproc.html"><img src="b_prev.gif" border="0" align=
+      "bottom" alt="Signal Pre-processing in LTPDA"></a>&nbsp;&nbsp;&nbsp;<a href=
+      "upsample.html"><img src="b_next.gif" border="0" align=
+      "bottom" alt="Upsampling data"></a></td>
+    </tr>
+  </table>
+
+  <h1 class="title"><a name="f3-12899" id="f3-12899"></a>Downsampling data</h1>
+  <hr>
+  
+  <p>
+	<h2>Description</h2>
+<p>
+  Downsampling is the process of reducing the sampling rate of a signal. <a href="matlab:doc('ao/downsample')"><tt>Downsample</tt></a> 
+  reduces the sampling rate of the input AOs by an integer factor by picking up one out of N samples. 
+  Note that no anti-aliasing filter is applied to the original data. Moreover, a <tt>offset</tt> can be 
+  specified, i.e., the sample at which the output data starts ---see examples below.
+</p>
+<h2>Syntax</h2>
+<div class="fragment"><pre>
+    <br>
+    b = downsample(a, pl)
+  </pre>
+</div>
+<h2>Parameters</h2>
+<p>  The following parameters can be set in this method:
+  <ul>
+    <li> <tt>factor</tt> - decimation factor [by default is 1: no downsampling] (must be an integer) </li>
+    <li> <tt>offset</tt> - sample offset for decimation </li>
+  </ul>
+</p>
+<p>
+  <h2>Examples</h2>
+</p>
+<p>
+  1. Downsampling a sequence of random data at original sampling rate of 10 Hz by a factor of 4 (<tt>fsout</tt> = 2.5 Hz) and no <tt>offset</tt>.
+</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)
+    pl_down = plist(<span class="string">'factor'</span>, 4);     <span class="comment">% add the decimation factor</span>
+    y       = downsample(x, pl_down); <span class="comment">% downsample the input AO, x</span>
+    iplot(x, y)
+  </pre>
+</div>
+
+<img src="images/downsample1.png" alt="Downsample" border="0">
+
+<p>
+  2. Downsampling a sequence of random data at original sampling rate of 10 Hz by a factor of 4 (<tt>fsout</tt> = 2.5 Hz) and <tt>offset</tt> = 10.
+</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)
+    pl_downoff = plist(<span class="string">'factor'</span>, 4,<span class="string">'offset'</span>,10);  <span class="comment">% add the decimation factor and the offset parameter</span>
+    y          = downsample(x, pl_downoff);       <span class="comment">% downsample the input AO, x</span>
+    iplot(x, y)
+  </pre>
+</div>
+
+<img src="images/downsample2.png" alt="Downsample" border="0">
+
+  </p>
+
+  <br>
+  <br>
+  <table class="nav" summary="Navigation aid" border="0" width=
+  "100%" cellpadding="0" cellspacing="0">
+    <tr valign="top">
+      <td align="left" width="20"><a href="preproc.html"><img src=
+      "b_prev.gif" border="0" align="bottom" alt=
+      "Signal Pre-processing in LTPDA"></a>&nbsp;</td>
+
+      <td align="left">Signal Pre-processing in LTPDA</td>
+
+      <td>&nbsp;</td>
+
+      <td align="right">Upsampling data</td>
+
+      <td align="right" width="20"><a href=
+      "upsample.html"><img src="b_next.gif" border="0" align=
+      "bottom" alt="Upsampling data"></a></td>
+    </tr>
+  </table><br>
+
+  <p class="copy">&copy;LTP Team</p>
+</body>
+</html>