Author: tn
Date: Thu May 31 23:34:46 2012
New Revision: 1344940
URL: http://svn.apache.org/viewvc?rev=1344940&view=rev
Log:
[MATH-644] cleanup of HypergeometricDistribution and symmetry fix for
upperCumulativeProbability, reported by marzieh.
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/distribution/HypergeometricDistribution.java
Modified:
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/distribution/HypergeometricDistribution.java
URL:
http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math3/distribution/HypergeometricDistribution.java?rev=1344940&r1=1344939&r2=1344940&view=diff
==============================================================================
---
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/distribution/HypergeometricDistribution.java
(original)
+++
commons/proper/math/trunk/src/main/java/org/apache/commons/math3/distribution/HypergeometricDistribution.java
Thu May 31 23:34:46 2012
@@ -21,7 +21,6 @@ import org.apache.commons.math3.exceptio
import org.apache.commons.math3.exception.NotStrictlyPositiveException;
import org.apache.commons.math3.exception.NumberIsTooLargeException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
-import org.apache.commons.math3.util.ArithmeticUtils;
import org.apache.commons.math3.util.FastMath;
/**
@@ -101,8 +100,7 @@ public class HypergeometricDistribution
} else if (x >= domain[1]) {
ret = 1.0;
} else {
- ret = innerCumulativeProbability(domain[0], x, 1, populationSize,
- numberOfSuccesses, sampleSize);
+ ret = innerCumulativeProbability(domain[0], x, 1);
}
return ret;
@@ -197,22 +195,6 @@ public class HypergeometricDistribution
}
/**
- * For this distribution, {@code X}, defined by the given hypergeometric
- * distribution parameters, this method returns {@code P(X = x)}.
- *
- * @param x Value at which the PMF is evaluated.
- * @param n the population size.
- * @param m number of successes in the population.
- * @param k the sample size.
- * @return PMF for the distribution.
- */
- private double probability(int n, int m, int k, int x) {
- return FastMath.exp(ArithmeticUtils.binomialCoefficientLog(m, x) +
- ArithmeticUtils.binomialCoefficientLog(n - m, k - x) -
- ArithmeticUtils.binomialCoefficientLog(n, k));
- }
-
- /**
* For this distribution, {@code X}, this method returns {@code P(X >= x)}.
*
* @param x Value at which the CDF is evaluated.
@@ -223,13 +205,12 @@ public class HypergeometricDistribution
double ret;
final int[] domain = getDomain(populationSize, numberOfSuccesses,
sampleSize);
- if (x < domain[0]) {
+ if (x <= domain[0]) {
ret = 1.0;
} else if (x > domain[1]) {
ret = 0.0;
} else {
- ret = innerCumulativeProbability(domain[1], x, -1, populationSize,
- numberOfSuccesses, sampleSize);
+ ret = innerCumulativeProbability(domain[1], x, -1);
}
return ret;
@@ -246,17 +227,13 @@ public class HypergeometricDistribution
* @param x1 Inclusive upper bound.
* @param dx Direction of summation (1 indicates summing from x0 to x1, and
* 0 indicates summing from x1 to x0).
- * @param n the population size.
- * @param m number of successes in the population.
- * @param k the sample size.
* @return {@code P(x0 <= X <= x1)}.
*/
- private double innerCumulativeProbability(int x0, int x1, int dx,
- int n, int m, int k) {
- double ret = probability(n, m, k, x0);
+ private double innerCumulativeProbability(int x0, int x1, int dx) {
+ double ret = probability(x0);
while (x0 != x1) {
x0 += dx;
- ret += probability(n, m, k, x0);
+ ret += probability(x0);
}
return ret;
}
