Alex Herbert created STATISTICS-51:
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Summary: Gamma ratio and delta ratio
Key: STATISTICS-51
URL: https://issues.apache.org/jira/browse/STATISTICS-51
Project: Apache Commons Statistics
Issue Type: New Feature
Components: gamma
Affects Versions: 1.1
Reporter: Alex Herbert
Fix For: 1.1
The recently ported gamma functions from the Boost C++ library contain a method
for computing a ratio of gamma functions:
{noformat}
gamma_ratio(a, b) = gamma(a) / gamma(b)
gamma_delta_ratio(a, delta) = gamma(a) / gamma(a + delta){noformat}
This method is required for part of the Boost C++ implementation of the
RegularizedBeta function.
It has an application in Commons Statistics for computing the mean and variance
of the [Nakagami
distribution|https://en.wikipedia.org/wiki/Nakagami_distribution].
Potential API:
{code:java}
// Added to the existing Gamma class
Gamma.ratio(a, b)
Gamma.delta_ratio(a, delta)
// New class
GammaRatio.value(a, b)
GammaRatio.delta(a, delta){code}
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