psteitz 2004/06/18 00:03:40
Modified: math/src/java/org/apache/commons/math/stat/univariate/moment
GeometricMean.java
Log:
Improved javadoc, implementation.
Revision Changes Path
1.19 +20 -15
jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/moment/GeometricMean.java
Index: GeometricMean.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/moment/GeometricMean.java,v
retrieving revision 1.18
retrieving revision 1.19
diff -u -r1.18 -r1.19
--- GeometricMean.java 27 Apr 2004 16:42:30 -0000 1.18
+++ GeometricMean.java 18 Jun 2004 07:03:40 -0000 1.19
@@ -21,7 +21,20 @@
/**
* Returns the <a href="http://www.xycoon.com/geometric_mean.htm";>
- * geometric mean </a> of the available values
+ * geometric mean </a> of the available values.
+ * <p>
+ * Uses [EMAIL PROTECTED] SumOfLogs} superclass to compute sum of logs and returns
+ * <code> exp( 1/n (sum of logs) ).</code> Therefore,
+ * <ul>
+ * <li>If any of values are < 0, the result is <code>NaN.</code></li>
+ * <li>If all values are non-negative and less than
<code>Double.POSITIVE_INFINITY</code>,
+ * but at least one value is 0, the result is <code>0.</code></li>
+ * <li>If both <code>Double.POSITIVE_INFINITY</code> and
+ * <code>Double.NEGATIVE_INFINITY</code> are among the values, the result is
+ * <code>NaN.</code></li>
+ * </ul>
+ *
+ *
* @version $Revision$ $Date$
*/
public class GeometricMean extends SumOfLogs implements Serializable{
@@ -29,15 +42,9 @@
/** Serializable version identifier */
static final long serialVersionUID = -8178734905303459453L;
- /** */
+ /**Number of values that have been added */
protected long n = 0;
- /** */
- private double geoMean = Double.NaN;
-
- /** */
- private double lastSum = 0.0;
-
/**
* @see
org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#increment(double)
*/
@@ -50,11 +57,11 @@
* @see
org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#getResult()
*/
public double getResult() {
- if (lastSum != super.getResult() || n == 1) {
- lastSum = super.getResult();
- geoMean = Math.exp(lastSum / (double) n);
+ if (n > 0) {
+ return Math.exp(super.getResult() / (double) n);
+ } else {
+ return Double.NaN;
}
- return geoMean;
}
/**
@@ -62,8 +69,6 @@
*/
public void clear() {
super.clear();
- lastSum = 0.0;
- geoMean = Double.NaN;
n = 0;
}
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