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<div class="subTitle">org.apache.commons.math3.complex</div>
<h2 title="Class RootsOfUnity" class="title">Class RootsOfUnity</h2>
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<pre>public class <span class="strong">RootsOfUnity</span>
extends <a href="http://docs.oracle.com/javase/6/docs/api/java/lang/Object.html?is-external=true" title="class or interface in java.lang">Object</a>
implements <a href="http://docs.oracle.com/javase/6/docs/api/java/io/Serializable.html?is-external=true" title="class or interface in java.io">Serializable</a></pre>
<div class="block">A helper class for the computation and caching of the <code>n</code>-th roots of
unity.</div>
<dl><dt><span class="strong">Since:</span></dt>
<dd>3.0</dd>
<dt><span class="strong">Version:</span></dt>
<dd>$Id: RootsOfUnity.java 1416643 2012-12-03 19:37:14Z tn $</dd>
<dt><span class="strong">See Also:</span></dt><dd><a href="../../../../../serialized-form.html#org.apache.commons.math3.complex.RootsOfUnity">Serialized Form</a></dd></dl>
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<td class="colOne"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#RootsOfUnity()">RootsOfUnity</a></strong>()</code>
<div class="block">Build an engine for computing the <code>n</code>-th roots of unity.</div>
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<td class="colFirst"><code>void</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#computeRoots(int)">computeRoots</a></strong>(int&nbsp;n)</code>
<div class="block">
Computes the <code>n</code>-th roots of unity.</div>
</td>
</tr>
<tr class="rowColor">
<td class="colFirst"><code>double</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#getImaginary(int)">getImaginary</a></strong>(int&nbsp;k)</code>
<div class="block">Get the imaginary part of the <code>k</code>-th <code>n</code>-th root of unity.</div>
</td>
</tr>
<tr class="altColor">
<td class="colFirst"><code>int</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#getNumberOfRoots()">getNumberOfRoots</a></strong>()</code>
<div class="block">Returns the number of roots of unity currently stored.</div>
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<tr class="rowColor">
<td class="colFirst"><code>double</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#getReal(int)">getReal</a></strong>(int&nbsp;k)</code>
<div class="block">Get the real part of the <code>k</code>-th <code>n</code>-th root of unity.</div>
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<td class="colFirst"><code>boolean</code></td>
<td class="colLast"><code><strong><a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#isCounterClockWise()">isCounterClockWise</a></strong>()</code>
<div class="block">Returns <code>true</code> if <a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#computeRoots(int)"><code>computeRoots(int)</code></a> was called with a
positive value of its argument <code>n</code>.</div>
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<pre>public&nbsp;RootsOfUnity()</pre>
<div class="block">Build an engine for computing the <code>n</code>-th roots of unity.</div>
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<h4>isCounterClockWise</h4>
<pre>public&nbsp;boolean&nbsp;isCounterClockWise()
throws <a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a></pre>
<div class="block">Returns <code>true</code> if <a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#computeRoots(int)"><code>computeRoots(int)</code></a> was called with a
positive value of its argument <code>n</code>. If <code>true</code>, then
counter-clockwise ordering of the roots of unity should be used.</div>
<dl><dt><span class="strong">Returns:</span></dt><dd><code>true</code> if the roots of unity are stored in
counter-clockwise order</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a></code> - if no roots of unity have been computed
yet</dd></dl>
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<h4>computeRoots</h4>
<pre>public&nbsp;void&nbsp;computeRoots(int&nbsp;n)
throws <a href="../../../../../org/apache/commons/math3/exception/ZeroException.html" title="class in org.apache.commons.math3.exception">ZeroException</a></pre>
<div class="block"><p>
Computes the <code>n</code>-th roots of unity. The roots are stored in
<code>omega[]</code>, such that <code>omega[k] = w ^ k</code>, where
<code>k = 0, ..., n - 1</code>, <code>w = exp(2 * pi * i / n)</code> and
<code>i = sqrt(-1)</code>.
</p>
<p>
Note that <code>n</code> can be positive of negative
</p>
<ul>
<li><code>abs(n)</code> is always the number of roots of unity.</li>
<li>If <code>n &gt; 0</code>, then the roots are stored in counter-clockwise order.</li>
<li>If <code>n &lt; 0</code>, then the roots are stored in clockwise order.</p>
</ul></div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>n</code> - the (signed) number of roots of unity to be computed</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/ZeroException.html" title="class in org.apache.commons.math3.exception">ZeroException</a></code> - if <code>n = 0</code></dd></dl>
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<h4>getReal</h4>
<pre>public&nbsp;double&nbsp;getReal(int&nbsp;k)
throws <a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a>,
<a href="../../../../../org/apache/commons/math3/exception/MathIllegalArgumentException.html" title="class in org.apache.commons.math3.exception">MathIllegalArgumentException</a></pre>
<div class="block">Get the real part of the <code>k</code>-th <code>n</code>-th root of unity.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>k</code> - index of the <code>n</code>-th root of unity</dd>
<dt><span class="strong">Returns:</span></dt><dd>real part of the <code>k</code>-th <code>n</code>-th root of unity</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a></code> - if no roots of unity have been
computed yet</dd>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/MathIllegalArgumentException.html" title="class in org.apache.commons.math3.exception">MathIllegalArgumentException</a></code> - if <code>k</code> is out of range</dd></dl>
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<h4>getImaginary</h4>
<pre>public&nbsp;double&nbsp;getImaginary(int&nbsp;k)
throws <a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a>,
<a href="../../../../../org/apache/commons/math3/exception/OutOfRangeException.html" title="class in org.apache.commons.math3.exception">OutOfRangeException</a></pre>
<div class="block">Get the imaginary part of the <code>k</code>-th <code>n</code>-th root of unity.</div>
<dl><dt><span class="strong">Parameters:</span></dt><dd><code>k</code> - index of the <code>n</code>-th root of unity</dd>
<dt><span class="strong">Returns:</span></dt><dd>imaginary part of the <code>k</code>-th <code>n</code>-th root of unity</dd>
<dt><span class="strong">Throws:</span></dt>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/MathIllegalStateException.html" title="class in org.apache.commons.math3.exception">MathIllegalStateException</a></code> - if no roots of unity have been
computed yet</dd>
<dd><code><a href="../../../../../org/apache/commons/math3/exception/OutOfRangeException.html" title="class in org.apache.commons.math3.exception">OutOfRangeException</a></code> - if <code>k</code> is out of range</dd></dl>
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<h4>getNumberOfRoots</h4>
<pre>public&nbsp;int&nbsp;getNumberOfRoots()</pre>
<div class="block">Returns the number of roots of unity currently stored. If
<a href="../../../../../org/apache/commons/math3/complex/RootsOfUnity.html#computeRoots(int)"><code>computeRoots(int)</code></a> was called with <code>n</code>, then this method
returns <code>abs(n)</code>. If no roots of unity have been computed yet, this
method returns 0.</div>
<dl><dt><span class="strong">Returns:</span></dt><dd>the number of roots of unity currently stored</dd></dl>
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