psteitz 2004/06/17 23:32:07
Modified: math/src/java/org/apache/commons/math/stat/univariate/summary
SumOfLogs.java
Log:
Improved efficiency and javadoc.
Revision Changes Path
1.18 +27 -28
jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/summary/SumOfLogs.java
Index: SumOfLogs.java
===================================================================
RCS file:
/home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/stat/univariate/summary/SumOfLogs.java,v
retrieving revision 1.17
retrieving revision 1.18
diff -u -r1.17 -r1.18
--- SumOfLogs.java 27 Apr 2004 16:42:32 -0000 1.17
+++ SumOfLogs.java 18 Jun 2004 06:32:07 -0000 1.18
@@ -17,16 +17,20 @@
import java.io.Serializable;
-import org
- .apache
- .commons
- .math
- .stat
- .univariate
- .AbstractStorelessUnivariateStatistic;
+import org.apache.commons.math.stat.univariate.AbstractStorelessUnivariateStatistic;
/**
- * Returns the sum of the natural logs for this collection of values.
+ * Returns the sum of the natural logs for this collection of values.
+ * <p>
+ * Uses [EMAIL PROTECTED] java.lang.Math#log(double)} to compute the logs.
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>Double.NEGATIVE_INFINITY.</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 $Revision$ $Date$
*/
@@ -35,27 +39,19 @@
/** Serializable version identifier */
static final long serialVersionUID = -370076995648386763L;
- /** */
+ /**Number of values that have been added */
private int n = 0;
/**
* The currently running value
*/
- private double value = Double.NaN;
-
- /** */
- private boolean init = true;
+ private double value = 0d;
/**
* @see
org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#increment(double)
*/
public void increment(final double d) {
- if (init) {
- value = Math.log(d);
- init = false;
- } else {
- value += Math.log(d);
- }
+ value += Math.log(d);
n++;
}
@@ -63,7 +59,11 @@
* @see
org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#getResult()
*/
public double getResult() {
- return value;
+ if (n > 0) {
+ return value;
+ } else {
+ return Double.NaN;
+ }
}
/**
@@ -77,23 +77,22 @@
* @see
org.apache.commons.math.stat.univariate.StorelessUnivariateStatistic#clear()
*/
public void clear() {
- value = Double.NaN;
- init = true;
+ value = 0d;
n = 0;
}
/**
- * Returns the sum of the natural logs for this collection of values
+ * Returns the sum of the natural logs for this collection of values.
+ * <p>
+ * See [EMAIL PROTECTED] SumOfLogs}.
+ *
* @param values Is a double[] containing the values
* @param begin processing at this point in the array
* @param length the number of elements to include
* @return the sumLog value or Double.NaN if the array is empty
* @see
org.apache.commons.math.stat.univariate.UnivariateStatistic#evaluate(double[], int,
int)
*/
- public double evaluate(
- final double[] values,
- final int begin,
- final int length) {
+ public double evaluate(final double[] values, final int begin, final int
length) {
double sumLog = Double.NaN;
if (test(values, begin, length)) {
sumLog = 0.0;
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