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<div class="section" id="signal-extension-modes">
<span id="reg-modes"></span><h1>Signal Extension Modes<a class="headerlink" href="#signal-extension-modes" title="Permalink to this headline">ΒΆ</a></h1>
<p>Import <a title="" class="reference external" href="../overview.html#module-pywt"><tt class="xref docutils literal"><span class="pre">pywt</span></tt></a> first</p>
<blockquote>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="kn">import</span> <span class="nn">pywt</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">def</span> <span class="nf">format_array</span><span class="p">(</span><span class="n">a</span><span class="p">):</span>
<span class="gp">... </span> <span class="sd">"""Consistent array representation across different systems"""</span>
<span class="gp">... </span> <span class="kn">import</span> <span class="nn">numpy</span>
<span class="gp">... </span> <span class="n">a</span> <span class="o">=</span> <span class="n">numpy</span><span class="o">.</span><span class="n">where</span><span class="p">(</span><span class="n">numpy</span><span class="o">.</span><span class="n">abs</span><span class="p">(</span><span class="n">a</span><span class="p">)</span> <span class="o"><</span> <span class="mf">1e-5</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">a</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">return</span> <span class="n">numpy</span><span class="o">.</span><span class="n">array2string</span><span class="p">(</span><span class="n">a</span><span class="p">,</span> <span class="n">precision</span><span class="o">=</span><span class="mi">5</span><span class="p">,</span> <span class="n">separator</span><span class="o">=</span><span class="s">' '</span><span class="p">,</span> <span class="n">suppress_small</span><span class="o">=</span><span class="bp">True</span><span class="p">)</span>
</pre></div>
</div>
</blockquote>
<p>List of availble signal extension <a class="reference external" href="../ref/signal-extension-modes.html#modes"><em>modes</em></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">print</span> <span class="n">pywt</span><span class="o">.</span><span class="n">MODES</span><span class="o">.</span><span class="n">modes</span>
<span class="go">['zpd', 'cpd', 'sym', 'ppd', 'sp1', 'per']</span>
</pre></div>
</div>
<p>Test that <a title="pywt.dwt" class="reference external" href="../ref/dwt-discrete-wavelet-transform.html#pywt.dwt"><tt class="xref docutils literal"><span class="pre">dwt()</span></tt></a> and <a title="pywt.idwt" class="reference external" href="../ref/idwt-inverse-discrete-wavelet-transform.html#pywt.idwt"><tt class="xref docutils literal"><span class="pre">idwt()</span></tt></a> can be performed using every mode:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">x</span> <span class="o">=</span> <span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">]</span>
<span class="gp">>>> </span><span class="k">for</span> <span class="n">mode</span> <span class="ow">in</span> <span class="n">pywt</span><span class="o">.</span><span class="n">MODES</span><span class="o">.</span><span class="n">modes</span><span class="p">:</span>
<span class="gp">... </span> <span class="n">cA</span><span class="p">,</span> <span class="n">cD</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"Mode:"</span><span class="p">,</span> <span class="n">mode</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"cA:"</span><span class="p">,</span> <span class="n">format_array</span><span class="p">(</span><span class="n">cA</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"cD:"</span><span class="p">,</span> <span class="n">format_array</span><span class="p">(</span><span class="n">cD</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"Reconstruction:"</span><span class="p">,</span> <span class="n">pywt</span><span class="o">.</span><span class="n">idwt</span><span class="p">(</span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="go">Mode: zpd</span>
<span class="go">cA: [-0.03468 1.73309 3.40612 6.32929 6.95095]</span>
<span class="go">cD: [-0.12941 -2.156 -5.95035 -1.21545 -1.8625 ]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: cpd</span>
<span class="go">cA: [ 1.2848 1.73309 3.40612 6.32929 7.51936]</span>
<span class="go">cD: [-0.48296 -2.156 -5.95035 -1.21545 0.25882]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: sym</span>
<span class="go">cA: [ 1.76777 1.73309 3.40612 6.32929 7.77817]</span>
<span class="go">cD: [-0.61237 -2.156 -5.95035 -1.21545 1.22474]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: ppd</span>
<span class="go">cA: [ 6.91627 1.73309 3.40612 6.32929 6.91627]</span>
<span class="go">cD: [-1.99191 -2.156 -5.95035 -1.21545 -1.99191]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: sp1</span>
<span class="go">cA: [-0.51764 1.73309 3.40612 6.32929 7.45001]</span>
<span class="go">cD: [ 0. -2.156 -5.95035 -1.21545 0. ]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: per</span>
<span class="go">cA: [ 4.05317 3.05257 2.85381 8.42522]</span>
<span class="go">cD: [ 0.18947 4.18258 4.33738 2.60428]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
</pre></div>
</div>
<p>Invalid mode name should rise a <tt class="xref docutils literal"><span class="pre">ValueError</span></tt>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">3</span><span class="p">,</span><span class="mi">4</span><span class="p">],</span> <span class="s">'db2'</span><span class="p">,</span> <span class="s">'invalid'</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="nc">ValueError</span>: <span class="n-Identifier">Unknown mode name 'invalid'.</span>
</pre></div>
</div>
<p>You can also refer to modes via <a class="reference external" href="../ref/signal-extension-modes.html#modes"><em>MODES</em></a> class attributes:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="k">for</span> <span class="n">mode_name</span> <span class="ow">in</span> <span class="p">[</span><span class="s">'zpd'</span><span class="p">,</span> <span class="s">'cpd'</span><span class="p">,</span> <span class="s">'sym'</span><span class="p">,</span> <span class="s">'ppd'</span><span class="p">,</span> <span class="s">'sp1'</span><span class="p">,</span> <span class="s">'per'</span><span class="p">]:</span>
<span class="gp">... </span> <span class="n">mode</span> <span class="o">=</span> <span class="nb">getattr</span><span class="p">(</span><span class="n">pywt</span><span class="o">.</span><span class="n">MODES</span><span class="p">,</span> <span class="n">mode_name</span><span class="p">)</span>
<span class="gp">... </span> <span class="n">cA</span><span class="p">,</span> <span class="n">cD</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">([</span><span class="mi">1</span><span class="p">,</span><span class="mi">2</span><span class="p">,</span><span class="mi">1</span><span class="p">,</span><span class="mi">5</span><span class="p">,</span><span class="o">-</span><span class="mi">1</span><span class="p">,</span><span class="mi">8</span><span class="p">,</span><span class="mi">4</span><span class="p">,</span><span class="mi">6</span><span class="p">],</span> <span class="s">'db2'</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"Mode:"</span><span class="p">,</span> <span class="n">mode</span><span class="p">,</span> <span class="s">"(</span><span class="si">%s</span><span class="s">)"</span> <span class="o">%</span> <span class="n">mode_name</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"cA:"</span><span class="p">,</span> <span class="n">format_array</span><span class="p">(</span><span class="n">cA</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"cD:"</span><span class="p">,</span> <span class="n">format_array</span><span class="p">(</span><span class="n">cD</span><span class="p">)</span>
<span class="gp">... </span> <span class="k">print</span> <span class="s">"Reconstruction:"</span><span class="p">,</span> <span class="n">pywt</span><span class="o">.</span><span class="n">idwt</span><span class="p">(</span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="n">mode</span><span class="p">)</span>
<span class="go">Mode: 0 (zpd)</span>
<span class="go">cA: [-0.03468 1.73309 3.40612 6.32929 6.95095]</span>
<span class="go">cD: [-0.12941 -2.156 -5.95035 -1.21545 -1.8625 ]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: 2 (cpd)</span>
<span class="go">cA: [ 1.2848 1.73309 3.40612 6.32929 7.51936]</span>
<span class="go">cD: [-0.48296 -2.156 -5.95035 -1.21545 0.25882]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: 1 (sym)</span>
<span class="go">cA: [ 1.76777 1.73309 3.40612 6.32929 7.77817]</span>
<span class="go">cD: [-0.61237 -2.156 -5.95035 -1.21545 1.22474]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: 4 (ppd)</span>
<span class="go">cA: [ 6.91627 1.73309 3.40612 6.32929 6.91627]</span>
<span class="go">cD: [-1.99191 -2.156 -5.95035 -1.21545 -1.99191]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: 3 (sp1)</span>
<span class="go">cA: [-0.51764 1.73309 3.40612 6.32929 7.45001]</span>
<span class="go">cD: [ 0. -2.156 -5.95035 -1.21545 0. ]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
<span class="go">Mode: 5 (per)</span>
<span class="go">cA: [ 4.05317 3.05257 2.85381 8.42522]</span>
<span class="go">cD: [ 0.18947 4.18258 4.33738 2.60428]</span>
<span class="go">Reconstruction: [ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
</pre></div>
</div>
<p>Some invalid mode values:</p>
<blockquote>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="o">-</span><span class="mi">1</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="nc">ValueError</span>: <span class="n-Identifier">Invalid mode.</span>
<span class="gp">>>> </span><span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="mi">7</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="nc">ValueError</span>: <span class="n-Identifier">Invalid mode.</span>
</pre></div>
</div>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="bp">None</span><span class="p">)</span>
<span class="gt">Traceback (most recent call last):</span>
<span class="c">...</span>
<span class="nc">TypeError</span>: <span class="n-Identifier">expected string or Unicode object, NoneType found</span>
</pre></div>
</div>
</blockquote>
<p>The default mode is <a class="reference external" href="../ref/signal-extension-modes.html#modes-sym"><em>sym</em></a>:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">cA</span>
<span class="go">[ 1.76776695 1.73309178 3.40612438 6.32928585 7.77817459]</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">cD</span>
<span class="go">[-0.61237244 -2.15599552 -5.95034847 -1.21545369 1.22474487]</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">pywt</span><span class="o">.</span><span class="n">idwt</span><span class="p">(</span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">)</span>
<span class="go">[ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
</pre></div>
</div>
<p>And using a keyword argument:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="gp">>>> </span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span> <span class="o">=</span> <span class="n">pywt</span><span class="o">.</span><span class="n">dwt</span><span class="p">(</span><span class="n">x</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">,</span> <span class="n">mode</span><span class="o">=</span><span class="s">'sym'</span><span class="p">)</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">cA</span>
<span class="go">[ 1.76776695 1.73309178 3.40612438 6.32928585 7.77817459]</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">cD</span>
<span class="go">[-0.61237244 -2.15599552 -5.95034847 -1.21545369 1.22474487]</span>
<span class="gp">>>> </span><span class="k">print</span> <span class="n">pywt</span><span class="o">.</span><span class="n">idwt</span><span class="p">(</span><span class="n">cA</span><span class="p">,</span> <span class="n">cD</span><span class="p">,</span> <span class="s">'db2'</span><span class="p">)</span>
<span class="go">[ 1. 2. 1. 5. -1. 8. 4. 6.]</span>
</pre></div>
</div>
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