psteitz 2004/07/20 15:29:51
Modified: math/xdocs/userguide utilities.xml
Log:
Added *last* missing sections :-)
Revision Changes Path
1.9 +54 -3 jakarta-commons/math/xdocs/userguide/utilities.xml
Index: utilities.xml
===================================================================
RCS file: /home/cvs/jakarta-commons/math/xdocs/userguide/utilities.xml,v
retrieving revision 1.8
retrieving revision 1.9
diff -u -r1.8 -r1.9
--- utilities.xml 17 May 2004 05:58:35 -0000 1.8
+++ utilities.xml 20 Jul 2004 22:29:50 -0000 1.9
@@ -39,7 +39,35 @@
<subsection name="6.2 Double array utilities" href="arrays">
<p>
- This is yet to be written. Any contributions will be gratefully accepted!
+ To maintain statistics based on a "rolling" window of values, a resizable
+ array implementation was developed and is provided for reuse in the
+ <code>util</code> package. The core functionality provided is described in
+ the documentation for the interface,
+ <a href="../apidocs/org/apache/commons/math/util/DoubleArray.html">
+ org.apache.commons.math.util.DoubleArray.</a> This interface adds one
+ method, <code>addElementRolling(double)</code> to basic list accessors.
+ The <code>addElementRolling</code> method adds an element
+ (the actual parameter) to the end of the list and removes the first element
+ in the list.
+ </p>
+ <p>
+ The <a href="../apidocs/org/apache/commons/math/util/ResizableDoubleArray.html">
+ org.apache.commons.math.util.ResizableDoubleArray</a> class provides a
+ configurable, array-backed implementation of the <code>DoubleArray</code>
+ interface. When <code>addElementRolling</code> is invoked, the underlying
+ array is expanded if necessary, the new element is added to the end of the
+ array and the "usable window" of the array is moved forward, so that
+ the first element is effectively discarded, what was the second becomes the
+ first, and so on. To efficiently manage storage, two maintenance
+ operations need to be periodically performed -- orphaned elements at the
+ beginning of the array need to be reclaimed and space for new elements at
+ the end needs to be created. Both of these operations are handled
+ automatically, with frequency / effect driven by the configuration
+ properties <code>expansionMode</code>, <code>expansionFactor</code> and
+ <code>contractionCriteria.</code> See
+ <a href="../apidocs/org/apache/commons/math/util/ResizableDoubleArray.html">
+ ResizableDoubleArray</a>
+ for details.
</p>
</subsection>
@@ -113,7 +141,30 @@
<subsection name="6.4 binomial coefficients, factorials and other common math
functions" href="math_utils">
<p>
- This is yet to be written. Any contributions will be gratefully accepted!
+ A collection of reusable math functions is provided in the
+ <a href="../apidocs/org/apache/commons/math/util/MathUtils.html">MathUtils</a>
+ utility class. MathUtils currently includes methods to compute the following:
<ul>
+ <li>
+ Binomial coeffiecients -- "n choose k" available as an (exact) long value,
+ <code>binomialCoefficient(int, int)</code> for small n, k; as a double,
+ <code>binomialCoefficientDouble(int, int)</code> for larger values; and in
+ a "super-sized" version, <code>binomialCoefficientLog(int, int)</code>
+ that returns the natural logarithm of the value.</li>
+ <li>
+ Factorials -- like binomial coefficients, these are available as exact long
+ values, <code>factorial(int)</code>; doubles,
+ <code>factorialDouble(int)</code>; or logs, <code>factorialLog(int)</code>.
</li>
+ <li>
+ Hyperbolic sine and cosine functions --
+ <code>cosh(double), sinh(double)</code></li>
+ <li>
+ sign (+1 if argument > 0, 0 if x = 0, and -1 if x < 0) and
+ indicator (+1.0 if argument >= 0 and -1.0 if argument < 0) functions
+ for variables of all primitive numeric types.</li>
+ <li>
+ a hash function, <code>hash(double),</code> returning a long-valued
+ hash code for a double value.
+ </li></ul>
</p>
</subsection>
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