[MATH-791] GammaDistribution.getAlpha() and getBeta() are confusing

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.1, 4.0
• Fix Version/s: 3.1
• Assignee: Sebastien Brisard
• Reporter: Sebastien Brisard
• Created: 21/May/12 18:35
• Updated: 04/Mar/13 18:53
• Resolved: 31/May/12 06:06

Description

As discussed on the mailing list

Some methods in o.a.c.m3.distribution.GammaDistribution are ill-named. Indeed, the class javadoc explicitly refers to the Wikipedia page. In this page, the shape parameter is named alpha and the scale parameter is 1 / beta
(inverse of beta), while in the current implementation, the shape parameter is named alpha, and the scale parameter is named beta (not 1 / beta !!!). This might be confusing. Looking at other web pages, I see there is apparently no consensus on the naming of shape and scale
parameters. The problem lies with the accessors, which are
double getAlpha()
double getBeta()

I think these accessors can lead to confusion. I would therefore propose to deprecate them, and replace them with
double getShape()
double getScale()