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Posted to dev@commons.apache.org by ps...@apache.org on 2004/09/01 17:51:40 UTC
cvs commit: jakarta-commons/math/src/java/org/apache/commons/math/stat StatUtils.java
psteitz 2004/09/01 08:51:40
Modified: math/src/java/org/apache/commons/math/stat StatUtils.java
Log:
Javadoc. Made assumption about precomputed mean in variance computations explicit.
Revision Changes Path
1.32 +13 -3 jakarta-commons/math/src/java/org/apache/commons/math/stat/StatUtils.java
Index: StatUtils.java
===================================================================
RCS file: /home/cvs/jakarta-commons/math/src/java/org/apache/commons/math/stat/StatUtils.java,v
retrieving revision 1.31
retrieving revision 1.32
diff -u -r1.31 -r1.32
--- StatUtils.java 17 Jul 2004 22:01:39 -0000 1.31
+++ StatUtils.java 1 Sep 2004 15:51:39 -0000 1.32
@@ -343,6 +343,11 @@
* See {@link org.apache.commons.math.stat.univariate.moment.Variance} for
* details on the computing algorithm.
* <p>
+ * The formula used assumes that the supplied mean value is the arithmetic
+ * mean of the sample data, not a known population parameter. This method
+ * is supplied only to save computation when the mean has already been
+ * computed.
+ * <p>
* Returns 0 for a single-value (i.e. length = 1) sample.
* <p>
* Throws <code>IllegalArgumentException</code> if the array is null or the
@@ -364,10 +369,15 @@
/**
* Returns the variance of the entries in the input array, using the
* precomputed mean value. Returns <code>Double.NaN</code> if the array
- * is empty.
+ * is empty.
* <p>
* See {@link org.apache.commons.math.stat.univariate.moment.Variance} for
- * details on the computing algorithm.
+ * details on the computing algorithm.
+ * <p>
+ * The formula used assumes that the supplied mean value is the arithmetic
+ * mean of the sample data, not a known population parameter. This method
+ * is supplied only to save computation when the mean has already been
+ * computed.
* <p>
* Returns 0 for a single-value (i.e. length = 1) sample.
* <p>
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