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<div class="subTitle">org.apache.ignite.ml.math</div>
<h2 title="Class Algebra" class="title">Class Algebra</h2>
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<pre>public class <span class="typeNameLabel">Algebra</span>
extends <a href="../../../../../org/apache/ignite/ml/math/Constants.html" title="class in org.apache.ignite.ml.math">Constants</a></pre>
<div class="block">Miscellaneous arithmetic and algebra functions.
Lifted from Apache Mahout.</div>
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<code><a href="../../../../../org/apache/ignite/ml/math/Constants.html#BIG">BIG</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#BIGINV">BIGINV</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#LOGPI">LOGPI</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#MACHEP">MACHEP</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#MAXGAM">MAXGAM</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#MAXLOG">MAXLOG</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#MINLOG">MINLOG</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#SQRTH">SQRTH</a>, <a href="../../../../../org/apache/ignite/ml/math/Constants.html#SQTPI">SQTPI</a></code></li>
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<td class="colOne"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#Algebra--">Algebra</a></span>()</code>&nbsp;</td>
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<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#binomial-double-long-">binomial</a></span>(double&nbsp;n,
long&nbsp;k)</code>
<div class="block">Efficiently returns the binomial coefficient, often also referred to as
"n over k" or "n choose k".</div>
</td>
</tr>
<tr id="i1" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#binomial-long-long-">binomial</a></span>(long&nbsp;n,
long&nbsp;k)</code>
<div class="block">Efficiently returns the binomial coefficient, often also referred to as "n over k" or "n choose k".</div>
</td>
</tr>
<tr id="i2" class="altColor">
<td class="colFirst"><code>static long</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#ceil-double-">ceil</a></span>(double&nbsp;val)</code>
<div class="block">Returns the smallest <code>long &gt;= value</code>.</div>
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<tr id="i3" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#chbevl-double-double:A-int-">chbevl</a></span>(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;N)</code>
<div class="block">Evaluates the series of Chebyshev polynomials Ti at argument x/2.</div>
</td>
</tr>
<tr id="i4" class="altColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#evalPoly-double-double:A-int-">evalPoly</a></span>(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;n)</code>
<div class="block">Evaluates the given polynomial of degree <code>N</code> at <code>x</code>.</div>
</td>
</tr>
<tr id="i5" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#evalPoly1-double-double:A-int-">evalPoly1</a></span>(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;n)</code>
<div class="block">Evaluates the given polynomial of degree <code>N</code> at <code>x</code>, assuming coefficient of N is 1.0.</div>
</td>
</tr>
<tr id="i6" class="altColor">
<td class="colFirst"><code>static long</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#floor-double-">floor</a></span>(double&nbsp;val)</code>
<div class="block">Returns the largest <code>long &lt;= value</code>.</div>
</td>
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<tr id="i7" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#hypot-double-double-">hypot</a></span>(double&nbsp;a,
double&nbsp;b)</code>
<div class="block">Gets <code>sqrt(a^2 + b^2)</code> without under/overflow.</div>
</td>
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<tr id="i8" class="altColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#log-double-double-">log</a></span>(double&nbsp;base,
double&nbsp;val)</code>
<div class="block">Returns <code>log&lt;sub&gt;base&lt;/sub&gt;value</code>.</div>
</td>
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<tr id="i9" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#log10-double-">log10</a></span>(double&nbsp;val)</code>
<div class="block">Returns <code>log&lt;sub&gt;10&lt;/sub&gt;value</code>.</div>
</td>
</tr>
<tr id="i10" class="altColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#log2-double-">log2</a></span>(double&nbsp;val)</code>
<div class="block">Returns <code>log&lt;sub&gt;2&lt;/sub&gt;value</code>.</div>
</td>
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<tr id="i11" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#logFactorial-int-">logFactorial</a></span>(int&nbsp;k)</code>
<div class="block">Returns <code>log(k!)</code>.</div>
</td>
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<tr id="i12" class="altColor">
<td class="colFirst"><code>static long</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#longFactorial-int-">longFactorial</a></span>(int&nbsp;k)</code>
<div class="block">Instantly returns the factorial <code>k!</code>.</div>
</td>
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<tr id="i13" class="rowColor">
<td class="colFirst"><code>static double</code></td>
<td class="colLast"><code><span class="memberNameLink"><a href="../../../../../org/apache/ignite/ml/math/Algebra.html#stirlingCorrection-int-">stirlingCorrection</a></span>(int&nbsp;k)</code>
<div class="block">Returns the StirlingCorrection.</div>
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<h4>Algebra</h4>
<pre>public&nbsp;Algebra()</pre>
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<h4>binomial</h4>
<pre>public static&nbsp;double&nbsp;binomial(double&nbsp;n,
long&nbsp;k)</pre>
<div class="block">Efficiently returns the binomial coefficient, often also referred to as
"n over k" or "n choose k". The binomial coefficient is defined as
<code>(n * n-1 * ... * n-k+1 ) / ( 1 * 2 * ... * k )</code>.
<ul> <li><code>k&amp;lt;0</code>: <code>0</code>.</li>
<li><code>k==0</code>: <code>1</code>.</li>
<li><code>k==1</code>: <code>n</code>.</li>
<li>else: <code>(n * n-1 * ... * n-k+1 ) / ( 1 * 2 * ... * k)</code>.</li>
</ul></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>n</code> - Size of set.</dd>
<dd><code>k</code> - Size of subset.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>Binomial coefficient.</dd>
</dl>
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<h4>binomial</h4>
<pre>public static&nbsp;double&nbsp;binomial(long&nbsp;n,
long&nbsp;k)</pre>
<div class="block">Efficiently returns the binomial coefficient, often also referred to as "n over k" or "n choose k".
The binomial coefficient is defined as
<ul> <li><code>k&amp;lt;0</code>: <code>0</code>. <li><code>k==0 || k==n</code>: <code>1</code>. <li><code>k==1 || k==n-1</code>:
<code>n</code>. <li>else: <code>(n * n-1 * ... * n-k+1 ) / ( 1 * 2 * ... * k )</code>. </ul></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>n</code> - Size of set.</dd>
<dd><code>k</code> - Size of subset.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>Binomial coefficient.</dd>
</dl>
</li>
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<h4>ceil</h4>
<pre>public static&nbsp;long&nbsp;ceil(double&nbsp;val)</pre>
<div class="block">Returns the smallest <code>long &gt;= value</code>.
<dl><dt>Examples: <code>1.0 -&gt; 1, 1.2 -&gt; 2, 1.9 -&gt; 2</code>. This
method is safer than using (long) Math.ceil(value), because of possible rounding error.</dt></dl></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>val</code> - Value for ceil.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>Ceil of the given value.</dd>
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<h4>chbevl</h4>
<pre>public static&nbsp;double&nbsp;chbevl(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;N)</pre>
<div class="block">Evaluates the series of Chebyshev polynomials Ti at argument x/2. The series is given by
<pre class="snippet">
N-1
- '
y = &gt; coef[i] T (x/2)
- i
i=0
</pre>
Coefficients are stored in reverse order, i.e. the zero order term is last in the array. Note N is the number of
coefficients, not the order.
<p>
If coefficients are for the interval a to b, x must have been transformed to x
-&lt; 2(2x - b - a)/(b-a) before entering the routine. This maps x from (a, b) to (-1, 1), over which the
Chebyshev polynomials are defined.</p>
<p>
If the coefficients are for the inverted interval, in which (a, b) is
mapped to (1/b, 1/a), the transformation required is <code>x -&gt; 2(2ab/x - b - a)/(b-a)</code>. If b is infinity, this
becomes <code>x -&gt; 4a/x - 1</code>.</p>
<p>
SPEED:
</p>
Taking advantage of the recurrence properties of the Chebyshev
polynomials, the routine requires one more addition per loop than evaluating a nested polynomial of the same
degree.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>x</code> - Argument to the polynomial.</dd>
<dd><code>coef</code> - Coefficients of the polynomial.</dd>
<dd><code>N</code> - Number of coefficients.</dd>
</dl>
</li>
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<h4>floor</h4>
<pre>public static&nbsp;long&nbsp;floor(double&nbsp;val)</pre>
<div class="block">Returns the largest <code>long &lt;= value</code>.
<dl><dt>Examples: <code>1.0 -&gt; 1, 1.2 -&gt; 1, 1.9 -&gt; 1 &lt;dt&gt; 2.0 -&gt; 2, 2.2 -&gt; 2, 2.9 -&gt; 2</code></dt></dl>
This method is safer than using (long) Math.floor(value), because of possible rounding error.</div>
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<h4>log</h4>
<pre>public static&nbsp;double&nbsp;log(double&nbsp;base,
double&nbsp;val)</pre>
<div class="block">Returns <code>log&lt;sub&gt;base&lt;/sub&gt;value</code>.</div>
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<pre>public static&nbsp;double&nbsp;log10(double&nbsp;val)</pre>
<div class="block">Returns <code>log&lt;sub&gt;10&lt;/sub&gt;value</code>.</div>
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<pre>public static&nbsp;double&nbsp;log2(double&nbsp;val)</pre>
<div class="block">Returns <code>log&lt;sub&gt;2&lt;/sub&gt;value</code>.</div>
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<h4>logFactorial</h4>
<pre>public static&nbsp;double&nbsp;logFactorial(int&nbsp;k)</pre>
<div class="block">Returns <code>log(k!)</code>. Tries to avoid overflows. For <code>k&amp;lt;30</code> simply looks up a table in O(1).
For <code>k&amp;gt;=30</code> uses Stirling's approximation.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>k</code> - must hold <code>k &amp;gt;= 0</code>.</dd>
</dl>
</li>
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<h4>longFactorial</h4>
<pre>public static&nbsp;long&nbsp;longFactorial(int&nbsp;k)</pre>
<div class="block">Instantly returns the factorial <code>k!</code>.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>k</code> - must hold <code>k &gt;= 0 &amp;&amp; k &lt; 21</code></dd>
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<h4>stirlingCorrection</h4>
<pre>public static&nbsp;double&nbsp;stirlingCorrection(int&nbsp;k)</pre>
<div class="block">Returns the StirlingCorrection.
<p>
Correction term of the Stirling approximation for <code>log(k!)</code> (series in
1/k, or table values for small k) with int parameter k. <code>log k! = (k + 1/2)log(k + 1) - (k + 1) +
(1/2)log(2Pi) + STIRLING_CORRECTION(k + 1) log k! = (k + 1/2)log(k) - k + (1/2)log(2Pi) +
STIRLING_CORRECTION(k) </code> </p></div>
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<h4>evalPoly1</h4>
<pre>public static&nbsp;double&nbsp;evalPoly1(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;n)</pre>
<div class="block">Evaluates the given polynomial of degree <code>N</code> at <code>x</code>, assuming coefficient of N is 1.0. Otherwise same
as <a href="../../../../../org/apache/ignite/ml/math/Algebra.html#evalPoly-double-double:A-int-"><code>evalPoly(double, double[], int)</code></a>.
<pre class="snippet">
2 N
y = C + C x + C x +...+ C x
0 1 2 N
</pre>
where <pre class="snippet">
C = 1
N
</pre>
and hence is omitted from the array.
<p>
Coefficients are stored in reverse order:</p>
<pre class="snippet">
coef[0] = C , ..., coef[N-1] = C .
N-1 0
</pre>
Calling arguments are otherwise the same as <a href="../../../../../org/apache/ignite/ml/math/Algebra.html#evalPoly-double-double:A-int-"><code>evalPoly(double, double[], int)</code></a>.
<p>
In the interest of speed, there are no checks for out of bounds arithmetic.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>x</code> - Argument to the polynomial.</dd>
<dd><code>coef</code> - Coefficients of the polynomial.</dd>
<dd><code>n</code> - Degree of the polynomial.</dd>
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<h4>evalPoly</h4>
<pre>public static&nbsp;double&nbsp;evalPoly(double&nbsp;x,
double[]&nbsp;coef,
int&nbsp;n)</pre>
<div class="block">Evaluates the given polynomial of degree <code>N</code> at <code>x</code>.
<pre class="snippet">
2 N
y = C + C x + C x +...+ C x
0 1 2 N
</pre>
<p>
Coefficients are stored in reverse order:</p>
<pre class="snippet">
coef[0] = C , ..., coef[N] = C .
N 0
</pre>
<p>
In the interest of speed, there are no checks for out of bounds arithmetic.</p></div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>x</code> - Argument to the polynomial.</dd>
<dd><code>coef</code> - Coefficients of the polynomial.</dd>
<dd><code>n</code> - Degree of the polynomial.</dd>
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<h4>hypot</h4>
<pre>public static&nbsp;double&nbsp;hypot(double&nbsp;a,
double&nbsp;b)</pre>
<div class="block">Gets <code>sqrt(a^2 + b^2)</code> without under/overflow.</div>
<dl>
<dt><span class="paramLabel">Parameters:</span></dt>
<dd><code>a</code> - First side value.</dd>
<dd><code>b</code> - Second side value.</dd>
<dt><span class="returnLabel">Returns:</span></dt>
<dd>Hypotenuse value.</dd>
</dl>
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<p class="legalCopy"><small><table width="100%" border="0" cellspacing=0 cellpadding=0 style="padding: 5px"> <tr> <td> <table style="padding-left: 0; margin: 0"> <tbody style="padding: 0; margin: 0"> <tr style="padding: 0; margin: 0"> <td> <a target=_blank href="https://ignite.apache.org"><nobr>2018 Copyright &#169; Apache Software Foundation</nobr></a> </td> </tr> </tbody> </table> </td> <td width="100%" align="right" valign="center"> <a href="https://twitter.com/ApacheIgnite" class="twitter-follow-button" data-show-count="false" data-size="large">Follow @ApacheIgnite</a> </td> </tr> <tr> <td colspan="2" valign="top" align="left"> <table style="padding-left: 0; margin: 0"> <tbody style="padding: 0; margin: 0"> <tr style="padding: 0; margin: 0"> <td> <b>Ignite Fabric</b> </td> <td>:&nbsp;&nbsp; ver. <strong>2.5.0</strong> </td> </tr> <tr style="padding: 0; margin: 0"> <td> <b>Release Date</b> </td> <td>:&nbsp;&nbsp; May 23 2018 </td> </tr> </tbody> </table> </td> </tr> </table></small></p>
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