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Cached DistributionFactory instance used to create TDistribution instances. 

git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/math/trunk@141283 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Phil Steitz 2004-06-06 22:28:25 +00:00
parent e571567af9
commit d8a43bf62a
1 changed files with 17 additions and 4 deletions
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21
src/java/org/apache/commons/math/stat/inference/TTestImpl.java
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@ -24,10 +24,13 @@ import org.apache.commons.math.stat.univariate.StatisticalSummary;
/**
* Implements t-test statistics defined in the {@link TTest} interface.
*
* @version $Revision: 1.5 $ $Date: 2004/06/02 13:08:55 $
* @version $Revision: 1.6 $ $Date: 2004/06/06 22:28:25 $
*/
public class TTestImpl implements TTest {
/** Cached DistributionFactory used to create TDistribution instances */
private DistributionFactory distributionFactory = null;
public TTestImpl() {
super();
}
@ -693,6 +696,16 @@ public class TTestImpl implements TTest {
//----------------------------------------------- Protected methods
/**
* Gets a DistributionFactory to use in creating TDistribution instances.
*/
protected DistributionFactory getDistributionFactory() {
if (distributionFactory == null) {
distributionFactory = DistributionFactory.newInstance();
}
return distributionFactory;
}
/**
* Computes approximate degrees of freedom for 2-sample t-test.
*
@ -757,8 +770,8 @@ public class TTestImpl implements TTest {
protected double tTest(double m, double mu, double v, double n)
throws MathException {
double t = Math.abs(t(m, mu, v, n));
TDistribution tDistribution =
DistributionFactory.newInstance().createTDistribution(n - 1);
TDistribution tDistribution =
getDistributionFactory().createTDistribution(n - 1);
return 1.0 - tDistribution.cumulativeProbability(-t, t);
}
@ -788,7 +801,7 @@ public class TTestImpl implements TTest {
degreesOfFreedom= df(v1, v2, n1, n2);
}
TDistribution tDistribution =
DistributionFactory.newInstance().createTDistribution(degreesOfFreedom);
getDistributionFactory().createTDistribution(degreesOfFreedom);
return 1.0 - tDistribution.cumulativeProbability(-t, t);
}
}