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Filled in missing Frequency section. 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141117 13f79535-47bb-0310-9956-ffa450edef68
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Phil Steitz 2004-03-06 20:43:00 +00:00
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@ -17,7 +17,7 @@
-->
<?xml-stylesheet type="text/xsl" href="./xdoc.xsl"?>
<!-- $Revision: 1.10 $ $Date: 2004/03/03 02:32:25 $ -->
<!-- $Revision: 1.11 $ $Date: 2004/03/06 20:43:00 $ -->
<document url="stat.html">
<properties>
<title>The Commons Math User Guide - Statistics</title>
@ -170,8 +170,66 @@ in.close();
</subsection>
<subsection name="1.3 Frequency distributions" href="frequency">
<p>This is yet to be written. Any contributions will be gratefully
accepted!</p>
<p>
<a href="../apidocs/org/apache/commons/math/stat/Frequency.html">
org.apache.commons.math.stat.univariate.Frequency</a>
provides a simple interface for maintaining counts and percentages of discrete
values.
</p>
<p>
Strings, integers, longs, chars are all supported as value types, as well as instances
of any class that implements <code>Comparable.</code> The ordering of values
used in computing cumulative frequencies is by default the <i>natural ordering,</i>
but this can be overriden by supplying a <code>Comparator</code> to the constructor.
Adding values that are not comparable to those that have already been added results in an
<code>IllegalArgumentException.</code>
</p>
<p>
Here are some examples.
<dl>
<dt>Compute a frequency distribution based on integer values</dt>
<br></br>
<dd>Mixing integers, longs, Integers and Longs:
<source>
Frequency f = new Frequency();
f.addValue(1);
f.addValue(new Integer(1));
f.addValue(new Long(1));
f.addValue(2)
f.addValue(new Integer(-1));
System.out.prinltn(f.getCount(1)); // displays 3
System.out.println(f.getCumPct(0)); // displays 0.2
System.out.println(f.getPct(new Integer(1))); // displays 0.6
System.out.println(f.getCumPct(-2)); // displays 0 -- all values are greater than this
System.out.println(f.getCumPct(10)); // displays 1 -- all values are less than this
</source>
</dd>
<dt>Count string frequencies</dt>
<br></br>
<dd>Using case-sensitive comparison, alpha sort order (natural comparator):
<source>
Frequency f = new Frequency();
f.addValue("one");
f.addValue("One");
f.addValue("oNe");
f.addValue("Z");
System.out.println(f.getCount("one")); // displays 1
System.out.println(f.getCumPct("Z")); // displays 0.5 -- second in sort order
</source>
</dd>
<dd>Using case-insensitive comparator:
<source>
Frequency f = new Frequency(String.CASE_INSENSITIVE_ORDER);
f.addValue("one");
f.addValue("One");
f.addValue("oNe");
f.addValue("Z");
System.out.println(f.getCount("one")); // displays 3
System.out.println(f.getCumPct("z")); // displays 1 -- last value
</source>
</dd>
</dl>
</p>
</subsection>
<subsection name="1.4 Bivariate regression" href="regression">
<p>This is yet to be written. Any contributions will be gratefully