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:[EMAIL PROTECTED] > 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, chi-squared, 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 chi-squared are separate from gamma to provide access > only to the parameters specific to each distribution. > > In chi-squared case, extension could have easily been use but this would > have exposed the alpha and beta properties in chi-squared. 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 chi-squared > properties. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
