I agree with all points below. It occured to me later this AM that exposing the right parameters
meant that the implementations needed to be separate. I now agree with you and Mark that
this would be too tricky to implement correctly while presenting the right interface to the
user.
What is you opinion on the DiscreteDistribution int vs. double issue?
Phil
Original Message
From: Brent Worden [mailto:brent@worden.org]
Sent: Wed 10/13/2004 2:08 PM
To: Jakarta Commons Developers List
Cc:
Subject: Re: [math] Questions regarding probability distributions
Here's my basis for the exponential, chisquared, and gamma distribution design (forgive
me for reiterating some points made by others):
Exponential is separate because both the CDF and inverse CDF have closed form computations.
This provides better performance and higher accuracy than the iterative method approximation.
Both exponential and chisquared are separate from gamma to provide access only to the parameters
specific to each distribution.
In chisquared case, extension could have easily been use but this would have exposed the
alpha and beta properties in chisquared. This would allow users to modify the properties
in an uncontrolled fashion, possibly resulting in a disfunctional distribution. Thus, encapsulation
was used to hide the gamma properties and only expose the relavent chisquared properties.

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