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http://issues.apache.org/bugzilla/show_bug.cgi?id=31688 Proposal for Poisson distributuion ------- Additional Comments From [EMAIL PROTECTED] 2004-11-02 01:37 ------- Few comments: 1) The createFormat method uses replaceAll, a JDK 1.4 call. I think [math] is meant to be compatible with JDK 1.3 if not JDK 1.2. 2) I see createFormat is being used to force precision on the inverse cumulative probs. Is there a reason this is being done on intermediate results? Is it necessary at all? 3) For the probability method, I would suggest using the ol' Exp[Log[f(x)]] trick to avoid numerical overflow. n! is a very volatile method for even moderate n values. 4) Can the parameter be renamed to something a little more descriptive? I would suggest mean. 5) I think the cumulative probability method can be optimized one of two ways, or by utilizing both. Cumulative probabilities for Poisson can be expressed in terms of the regularized gamma function which we already have implemented. The performance of this approach would not deteriorate for large x as the current loop does. At a minimum, instead of making calls to probability for each summation term, the ratio of successive terms should be used to alleviate the need to call n! for every term. 6) Is there a compelling reason not to use the inverseCumulativeProbability method provided by the AbstractDiscreteDistribution class? --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
