Yes you're right, with the parametrization model you're using it would
probably be confusing to simply let the exponential and chisquared
distributions be instances of a gammadistribution. However, this indicates
that there may be something flawed here. Remember, the chisquared
distribution *is a* gammadistribution, and this should be reflected in the
inheritance structure. Basically, you need some means to express
relationships between probability distributions.
> 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.
>
>
> 
> To unsubscribe, email: commonsdevunsubscribe@jakarta.apache.org
> For additional commands, email: commonsdevhelp@jakarta.apache.org

To unsubscribe, email: commonsdevunsubscribe@jakarta.apache.org
For additional commands, email: commonsdevhelp@jakarta.apache.org
