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Added geometric mean to StatUtils. 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141392 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2004-07-17 22:01:39 +00:00
parent eb6fb6cda4
commit 219db32c27
2 changed files with 60 additions and 3 deletions
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48
src/java/org/apache/commons/math/stat/StatUtils.java
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@ -16,6 +16,7 @@
package org.apache.commons.math.stat;
import org.apache.commons.math.stat.univariate.UnivariateStatistic;
import org.apache.commons.math.stat.univariate.moment.GeometricMean;
import org.apache.commons.math.stat.univariate.moment.Mean;
import org.apache.commons.math.stat.univariate.moment.Variance;
import org.apache.commons.math.stat.univariate.rank.Max;
@ -30,7 +31,7 @@ import org.apache.commons.math.stat.univariate.summary.SumOfSquares;
* StatUtils provides static methods for computing statistics based on data
* stored in double[] arrays.
*
* @version $Revision: 1.30 $ $Date: 2004/07/11 18:41:19 $
* @version $Revision: 1.31 $ $Date: 2004/07/17 22:01:39 $
*/
public final class StatUtils {
@ -58,8 +59,11 @@ public final class StatUtils {
/** variance */
private static Variance variance = new Variance();
/** variance */
/** percentile */
private static Percentile percentile = new Percentile();
/** geometric mean */
private static GeometricMean geometricMean = new GeometricMean();
/**
* Private Constructor
@ -246,6 +250,46 @@ public final class StatUtils {
final int length) {
return mean.evaluate(values, begin, length);
}
/**
* Returns the geometric mean of the entries in the input array, or
* <code>Double.NaN</code> if the array is empty.
* <p>
* Throws <code>IllegalArgumentException</code> if the array is null.
* <p>
* See {@link org.apache.commons.math.stat.univariate.moment.GeometricMean}
* for details on the computing algorithm.
*
* @param values the input array
* @return the geometric mean of the values or Double.NaN if the array is empty
* @throws IllegalArgumentException if the array is null
*/
public static double geometricMean(final double[] values) {
return geometricMean.evaluate(values);
}
/**
* Returns the geometric mean of the entries in the specified portion of
* the input array, or <code>Double.NaN</code> if the designated subarray
* is empty.
* <p>
* Throws <code>IllegalArgumentException</code> if the array is null.
* <p>
* See {@link org.apache.commons.math.stat.univariate.moment.GeometricMean}
* for details on the computing algorithm.
*
* @param values the input array
* @param begin index of the first array element to include
* @param length the number of elements to include
* @return the geometric mean of the values or Double.NaN if length = 0
* @throws IllegalArgumentException if the array is null or the array index
* parameters are not valid
*/
public static double geometricMean(final double[] values, final int begin,
final int length) {
return geometricMean.evaluate(values, begin, length);
}
/**
* Returns the variance of the entries in the input array, or

15
src/test/org/apache/commons/math/stat/StatUtilsTest.java
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@ -23,7 +23,7 @@ import org.apache.commons.math.TestUtils;
/**
* Test cases for the {@link StatUtils} class.
* @version $Revision: 1.18 $ $Date: 2004/07/11 18:42:07 $
* @version $Revision: 1.19 $ $Date: 2004/07/17 22:01:39 $
*/
public final class StatUtilsTest extends TestCase {
@ -372,4 +372,17 @@ public final class StatUtilsTest extends TestCase {
// expected
}
}
public void testGeometricMean() throws Exception {
double[] test = null;
try {
double x = StatUtils.geometricMean(test);
fail("Expecting IllegalArgumentException");
} catch (IllegalArgumentException ex) {
// expected
}
test = new double[] {2, 4, 6, 8};
assertEquals(Math.exp(0.25d * StatUtils.sumLog(test)),
StatUtils.geometricMean(test), Double.MIN_VALUE);
}
}