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aherbert pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-statistics.git
commit 7814866107e276446144acc14ba458b487473de2
Author: aherbert <aherb...@apache.org>
AuthorDate: Mon Sep 27 12:21:57 2021 +0100
Prevent p=0 in Pascal distribution
The Pascal is the sum of n independent random variables having an
identical geometric distribution with parameter p. The value p=0 is not
allowed in the Geometric distribution.
This value causes an error in mathematica and scipy stats. It creates
NaN values in R and Matlab.
---
.../distribution/PascalDistribution.java | 6 ++--
.../distribution/PascalDistributionTest.java | 32 +---------------------
2 files changed, 4 insertions(+), 34 deletions(-)
diff --git
a/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/PascalDistribution.java
b/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/PascalDistribution.java
index 164cec1..037147e 100644
---
a/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/PascalDistribution.java
+++
b/commons-statistics-distribution/src/main/java/org/apache/commons/statistics/distribution/PascalDistribution.java
@@ -67,7 +67,7 @@ public class PascalDistribution extends
AbstractDiscreteDistribution {
*
* @param r Number of successes.
* @param p Probability of success.
- * @throws IllegalArgumentException if {@code r <= 0} or {@code p < 0}
+ * @throws IllegalArgumentException if {@code r <= 0} or {@code p <= 0}
* or {@code p > 1}.
*/
public PascalDistribution(int r,
@@ -75,9 +75,9 @@ public class PascalDistribution extends
AbstractDiscreteDistribution {
if (r <= 0) {
throw new
DistributionException(DistributionException.NOT_STRICTLY_POSITIVE, r);
}
- if (p < 0 ||
+ if (p <= 0 ||
p > 1) {
- throw new
DistributionException(DistributionException.INVALID_PROBABILITY, p);
+ throw new
DistributionException(DistributionException.INVALID_NON_ZERO_PROBABILITY, p);
}
numberOfSuccesses = r;
diff --git
a/commons-statistics-distribution/src/test/java/org/apache/commons/statistics/distribution/PascalDistributionTest.java
b/commons-statistics-distribution/src/test/java/org/apache/commons/statistics/distribution/PascalDistributionTest.java
index 22ddd2c..f31f66a 100644
---
a/commons-statistics-distribution/src/test/java/org/apache/commons/statistics/distribution/PascalDistributionTest.java
+++
b/commons-statistics-distribution/src/test/java/org/apache/commons/statistics/distribution/PascalDistributionTest.java
@@ -94,37 +94,6 @@ class PascalDistributionTest extends
DiscreteDistributionAbstractTest {
//-------------------- Additional test cases
-------------------------------
- /** Test degenerate case p = 0. */
- @Test
- void testDegenerate0() {
- final PascalDistribution dist = new PascalDistribution(5, 0.0d);
- Assertions.assertEquals(0.0, dist.getProbabilityOfSuccess());
- Assertions.assertEquals(Double.POSITIVE_INFINITY, dist.getMean());
- Assertions.assertEquals(Double.POSITIVE_INFINITY, dist.getVariance());
-
- setDistribution(dist);
- setProbabilityTestPoints(new int[] {-1, 0, 1, 2, 5, 10});
- setProbabilityTestValues(new double[] {0.0, 0.0, 0.0, 0.0, 0.0, 0.0});
- setCumulativeTestPoints(new int[] {-1, 0, 1, 2, 5, 10});
- setCumulativeTestValues(new double[] {0.0, 0.0, 0.0, 0.0, 0.0, 0.0});
- setInverseCumulativeTestPoints(new double[] {0.1, 0.5, 1.0});
- setInverseCumulativeTestValues(new int[] {Integer.MAX_VALUE,
Integer.MAX_VALUE, Integer.MAX_VALUE});
- verifyProbabilities();
- verifyLogProbabilities();
- verifyCumulativeProbabilities();
- verifySurvivalProbability();
- verifySurvivalAndCumulativeProbabilityComplement();
- verifyInverseCumulativeProbabilities();
-
- Assertions.assertEquals(0, dist.getSupportLowerBound());
- Assertions.assertEquals(Integer.MAX_VALUE,
dist.getSupportUpperBound());
-
- final DiscreteDistribution.Sampler s =
dist.createSampler(RandomSource.SPLIT_MIX_64.create());
- for (int i = 0; i < 5; i++) {
- Assertions.assertEquals(Integer.MAX_VALUE, s.sample());
- }
- }
-
/** Test degenerate case p = 1. */
@Test
void testDegenerate1() {
@@ -172,6 +141,7 @@ class PascalDistributionTest extends
DiscreteDistributionAbstractTest {
"0, 0.5",
"-1, 0.5",
"3, -0.1",
+ "3, 0.0",
"3, 1.1",
})
void testConstructorPreconditions(int r, double p) {
