Hi All, Coming from discussion happened here https://issues.apache.org/jira/browse/NUMBERS-38
As Gamma is nothing but advanced factorial function gamma(n)=(n-1)! with advantages like we can have factorial of whole numbers as well as factional. Now as [Gamma functions ( https://en.wikipedia.org/wiki/Gamma_function ) which is having general formula {{Gamma( x ) = integral( t^(x-1) e^(-t), t = 0 .. infinity)}} is a plane old base function however Lanczos approximation / Stirling's approximation /Spouge's Approximation *is a* gamma function so they should be extend Gamma. Exact algorithm and formulas here : - Lanczo's Approximation - https://en.wikipedia.org/wiki/Lanczos_approximation - Stirling's Approximation - https://en.wikipedia.org/wiki/Stirling%27s_approximation - Spouge's Approximation - https://en.wikipedia.org/wiki/Spouge%27s_approximation Why to refactor code is because basic gamma function computes not so accurate/precision values so someone who need quick computation without precision can choose it, while someone who need precision overs cost of performance (Lanczos approximation is accurate so its slow takes more cpu cycle) can choose which algorithm they want. for some scientific application all values should be computed with great precision, with out Gamma class no choice is given for choosing which algorithm user want. I'm proposing to create something like: Gamma gammaFun = new Gamma(); gammaFun.value( x ); Gamma gammaFun = new LanczosGamma(); gammaFun.value( x ); Gamma gammaFun = new StirlingsGamma(); gammaFun.value( x ); Gamma gammaFun = new SpougesGamma(); gammaFun.value( x ); Also as the class name suggestion {{LanczosApproximation}} it should execute/implement full *Lanczos Algoritham* but we are just computing coefficients in that class which is incorrect, so just refactoring is needed which wont break any dependency of this class anywhere. (will modify code such way). let me know your thoughts? --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
