Hi Mikkel, > It seems like only the test was changed in r1210359 (svn diff -r > 1210359). This does _not_ correspond to the log (svn log -r 1210359).
Here is an excerpt of the email sent automatically when I committed revision 1210359 ==========BEGIN EXCERPT========== Author: celestin Date: Mon Dec 5 08:15:38 2011 New Revision: 1210359 URL: http://svn.apache.org/viewvc?rev=1210359&view=rev Log: - Corrected expressions for mean and variance in distribution.PascalDistribution (MATH-715). - Made javadoc more explicit - Restored SVN properties to various files in package distribution. .................... Modified: commons/proper/math/trunk/src/main/java/org/apache/commons/math/distribution/PascalDistribution.java URL: http://svn.apache.org/viewvc/commons/proper/math/trunk/src/main/java/org/apache/commons/math/distribution/PascalDistribution.java?rev=1210359&r1=1210358&r2=1210359&view=diff ============================================================================== --- commons/proper/math/trunk/src/main/java/org/apache/commons/math/distribution/PascalDistribution.java (original) +++ commons/proper/math/trunk/src/main/java/org/apache/commons/math/distribution/PascalDistribution.java Mon Dec 5 08:15:38 2011 @@ -31,10 +31,25 @@ import org.apache.commons.math.util.Fast * </p> * <p> * There are various ways to express the probability mass and distribution - * functions for the Pascal distribution. The convention employed by the - * library is to express these functions in terms of the number of failures in - * a Bernoulli experiment - * (see <a href="http://en.wikipedia.org/wiki/Negative_binomial_distribution#Waiting_time_in_a_Bernoulli_process";>Waiting Time in a Bernoulli Process</a>). + * functions for the Pascal distribution. The present implementation represents + * the distribution of the number of failures before {@code r} successes occur. + * This is the convention adopted in e.g. + * <a href="http://mathworld.wolfram.com/NegativeBinomialDistribution.html";>MathWorld</a>, + * but <em>not</em> in + * <a href="http://en.wikipedia.org/wiki/Negative_binomial_distribution";>Wikipedia</a>. + * </p> + * <p> + * For a random variable {@code X} whose values are distributed according to this + * distribution, the probability mass function is given by<br/> + * {@code P(X = k) = C(k + r - 1, r - 1) * p^r * (1 - p)^k,}<br/> + * where {@code r} is the number of successes, {@code p} is the probability of + * success, and {@code X} is the total number of failures. {@code C(n, k)} is + * the binomial coefficient ({@code n} choose {@code k}). The mean and variance + * of {@code X} are<br/> + * {@code E(X) = (1 - p) * r / p, var(X) = (1 - p) * r / p^2.}<br/> + * Finally, the cumulative distribution function is given by<br/> + * {@code P(X <= k) = I(p, r, k + 1)}, + * where I is the regularized incomplete Beta function. * </p> * * @see <a href="http://en.wikipedia.org/wiki/Negative_binomial_distribution";> @@ -159,25 +174,24 @@ public class PascalDistribution extends * {@inheritDoc} * * For number of successes {@code r} and probability of success {@code p}, - * the mean is {@code (r * p) / (1 - p)}. + * the mean is {@code r * (1 - p) / p}. */ public double getNumericalMean() { final double p = getProbabilityOfSuccess(); final double r = getNumberOfSuccesses(); - return (r * p) / (1 - p); + return (r * (1 - p)) / p; } /** * {@inheritDoc} * * For number of successes {@code r} and probability of success {@code p}, - * the variance is {@code (r * p) / (1 - p)^2}. + * the variance is {@code r * (1 - p) / p^2}. */ public double getNumericalVariance() { final double p = getProbabilityOfSuccess(); final double r = getNumberOfSuccesses(); - final double pInv = 1 - p; - return (r * p) / (pInv * pInv); + return r * (1 - p) / (p * p); } ==========END EXCERPT========== It seems to me that everything (?) is OK? > > It seems like the changes was done in r1210358. Is that true? > I don't think so (see extract below). ==========BEGIN EXCERPT========== Author: sgoeschl Date: Mon Dec 5 08:02:46 2011 New Revision: 1210358 URL: http://svn.apache.org/viewvc?rev=1210358&view=rev Log: [maven-release-plugin] prepare for next development iteration Modified: commons/proper/email/trunk/pom.xml ==========END EXCERPT========== I don't really understand what is happening. I hope I didn't mess up anything this morning. Please keep me posted. Sébastien --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
