Mercurial > hg > de.mpg.mpiwg.itgroup.digilib.plugin
diff libs/commons-math-2.1/docs/userguide/fraction.html @ 10:5f2c5fb36e93
commons-math-2.1 added
| author | dwinter |
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| date | Tue, 04 Jan 2011 10:00:53 +0100 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/libs/commons-math-2.1/docs/userguide/fraction.html Tue Jan 04 10:00:53 2011 +0100 @@ -0,0 +1,260 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> + + + + + + + + + + + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <title>Math - The Commons Math User Guide - Fractions</title> + <style type="text/css" media="all"> + @import url("../css/maven-base.css"); + @import url("../css/maven-theme.css"); + @import url("../css/site.css"); + </style> + <link rel="stylesheet" href="../css/print.css" type="text/css" media="print" /> + <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1" /> + </head> + <body class="composite"> + <div id="banner"> + <span id="bannerLeft"> + + Commons Math User Guide + + </span> + <div class="clear"> + <hr/> + </div> + </div> + <div id="breadcrumbs"> + + + + + + + + + <div class="xright"> + + + + + + + + </div> + <div class="clear"> + <hr/> + </div> + </div> + <div id="leftColumn"> + <div id="navcolumn"> + + + + + + + + + <h5>User Guide</h5> + <ul> + + <li class="none"> + <a href="../userguide/index.html">Contents</a> + </li> + + <li class="none"> + <a href="../userguide/overview.html">Overview</a> + </li> + + <li class="none"> + <a href="../userguide/stat.html">Statistics</a> + </li> + + <li class="none"> + <a href="../userguide/random.html">Data Generation</a> + </li> + + <li class="none"> + <a href="../userguide/linear.html">Linear Algebra</a> + </li> + + <li class="none"> + <a href="../userguide/analysis.html">Numerical Analysis</a> + </li> + + <li class="none"> + <a href="../userguide/special.html">Special Functions</a> + </li> + + <li class="none"> + <a href="../userguide/utilities.html">Utilities</a> + </li> + + <li class="none"> + <a href="../userguide/complex.html">Complex Numbers</a> + </li> + + <li class="none"> + <a href="../userguide/distribution.html">Distributions</a> + </li> + + <li class="none"> + <strong>Fractions</strong> + </li> + + <li class="none"> + <a href="../userguide/transform.html">Transform Methods</a> + </li> + + <li class="none"> + <a href="../userguide/geometry.html">3D Geometry</a> + </li> + + <li class="none"> + <a href="../userguide/optimization.html">Optimization</a> + </li> + + <li class="none"> + <a href="../userguide/ode.html">Ordinary Differential Equations</a> + </li> + + <li class="none"> + <a href="../userguide/genetics.html">Genetic Algorithms</a> + </li> + </ul> + <a href="http://maven.apache.org/" title="Built by Maven" class="poweredBy"> + <img alt="Built by Maven" src="../images/logos/maven-feather.png"></img> + </a> + + + + + + + + + </div> + </div> + <div id="bodyColumn"> + <div id="contentBox"> + <div class="section"><h2><a name="a9_Fractions"></a>9 Fractions</h2> +<div class="section"><h3><a name="a9.1_Overview"></a>9.1 Overview</h3> +<p> + The fraction packages provides a fraction number type as well as + fraction number formatting. + </p> +</div> +<div class="section"><h3><a name="a9.2_Fraction_Numbers"></a>9.2 Fraction Numbers</h3> +<p><a href="../apidocs/org/apache/commons/math/fraction/Fraction.html"> + org.apache.commons.math.fraction.Fraction</a> and + <a href="../apidocs/org/apache/commons/math/fraction/BigFraction.html"> + org.apache.commons.math.fraction.BigFraction</a> provide fraction number + type that forms the basis for the fraction functionality found in + commons-math. The former one can be used for fractions whose numerators + and denominators are small enough to fit in an int (taking care of intermediate + values) while the second class should be used when there is a risk the numerator + and denominator grow very large. + </p> +<p> + A fraction number, can be built from two integer arguments representing numerator + and denominator or from a double which will be approximated: + <div class="source"><pre>Fraction f = new Fraction(1, 3); // 1 / 3 +Fraction g = new Fraction(0.25); // 1 / 4</pre> +</div> +</p> +<p> + Of special note with fraction construction, when a fraction is created it is always reduced to lowest terms. + </p> +<p> + The <code>Fraction</code> class provides many unary and binary + fraction operations. These operations provide the means to add, + subtract, multiple and, divide fractions along with other functions similar to the real number functions found in + <code>java.math.BigDecimal</code>: + <div class="source"><pre>Fraction lhs = new Fraction(1, 3); +Fraction rhs = new Fraction(2, 5); + +Fraction answer = lhs.add(rhs); // add two fractions + answer = lhs.subtract(rhs); // subtract two fractions + answer = lhs.abs(); // absolute value + answer = lhs.reciprocal(); // reciprocal of lhs</pre> +</div> +</p> +<p> + Like fraction construction, for each of the fraction functions, the resulting fraction is reduced to lowest terms. + </p> +</div> +<div class="section"><h3><a name="a9.3_Fraction_Formatting_and_Parsing"></a>9.3 Fraction Formatting and Parsing</h3> +<p><code>Fraction</code> instances can be converted to and from strings + using the<a href="../apidocs/org/apache/commons/math/fraction/FractionFormat.html"> + org.apache.commons.math.fraction.FractionFormat</a> class. + <code>FractionFormat</code> is a <code>java.text.Format</code> + extension and, as such, is used like other formatting objects (e.g. + <code>java.text.SimpleDateFormat</code>): + <div class="source"><pre>FractionFormat format = new FractionFormat(); // default format +Fraction f = new Fraction(2, 4); +String s = format.format(f); // s contains "1 / 2", note the reduced fraction</pre> +</div> +</p> +<p> + To customize the formatting output, one or two + <code>java.text.NumberFormat</code> instances can be used to construct + a <code>FractionFormat</code>. These number formats control the + formatting of the numerator and denominator of the fraction: + <div class="source"><pre>NumberFormat nf = NumberFormat.getInstance(Locale.FRANCE); +// create fraction format with custom number format +// when one number format is used, both numerator and +// denominator are formatted the same +FractionFormat format = new FractionFormat(nf); +Fraction f = new Fraction(2000, 3333); +String s = format.format(c); // s contains "2.000 / 3.333" + +NumberFormat nf2 = NumberFormat.getInstance(Locale.US); +// create fraction format with custom number formats +format = new FractionFormat(nf, nf2); +s = format.format(f); // s contains "2.000 / 3,333"</pre> +</div> +</p> +<p> + Formatting's inverse operation, parsing, can also be performed by + <code>FractionFormat</code>. To parse a fraction from a string, + simply call the <code>parse</code> method: + <div class="source"><pre>FractionFormat ff = new FractionFormat(); +Fraction f = ff.parse("-10 / 21");</pre> +</div> +</p> +</div> +</div> + + </div> + </div> + <div class="clear"> + <hr/> + </div> + <div id="footer"> + <div class="xright">© + 2003-2010 + + + + + + + + + + </div> + <div class="clear"> + <hr/> + </div> + </div> + </body> +</html>