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From Phil Steitz <phil.ste...@gmail.com>
Subject Re: [Math] Package "o.a.c.m.distribution"
Date Tue, 31 Jul 2012 18:52:07 GMT
On 7/31/12 3:34 AM, Dennis Hendriks wrote:
> See answers below.
>
> On 07/31/2012 12:00 PM, Gilles Sadowski wrote:
>> On Tue, Jul 31, 2012 at 08:18:13AM +0200, Dennis Hendriks wrote:
>>>> * Why doesn't "KolmogorovSmirnovDistribution" implement one of the
>>>>     interfaces of the package (and/or inherit from an abstract
>>>> class)?
>>>
>>> See also:
>>> http://apache-commons.680414.n4.nabble.com/math-KolmogorovSmirnovDistribution-not-part-of-the-distribution-hierarchy-td4114395.html
>>
>> Thanks for digging that thread out.
>> Do I rightly deduce that it is unfinished work, which should give
>> rise to a
>> JIRA ticket?
>
> That would be my guess.

Yep.  Per the tread above, the reason this class exists is to enable
Kolmogorov-Smirnov tests, which it pretty much does.  See MATH-437. 
I have no idea how to implement the missing distribution methods or
if anyone would ever use them if we did, so it may be better to just
move this class to .stat.inference, which is what it is really for.
  Making it package scope there and adding a class with some doco
and wrapper methods to make setting up and executing K-S tests would
likely be more valuable than trying to fill out the distribution
methods.  Of course, if anyone has ideas on how to implement the
missing methods, patches are welcome :)
>
>>>> * Why is method "probability(double)" part of the
>>>> "RealDistribution"
>>>>     interface? [All implementations return 0.]
>>>
>>> My guess would be that it is left over from when integer and real
>>> distributions shared a common hierarchy.
>>
>> I would agree with the guess.
>> Does everyone agree to deprecate this method (in 3.1) and remove
>> it (in
>> 4.0)?
>
> +1
-0 - Without this, we can't represent non-discrete distributions
that assign positive mass to singletons.  Could be no big loss, but
in the archives there is discussion of non-continuous distributions,
which such a beast would have to be, and I think we agreed that we
want to be able to support / represent them.  We have split
distributions into Integer (which really means discrete) and "Real"
(which means essentially everything else).  So basically while all
currently implemented real distributions have probability(-)
identically zero, there are (non-discrete) distributions over the
reals that do not have this property and we may want to enable users
to represent them.  Could be these cases are so non-standard as to
not be worth worrying about; but I don't see harm in leaving the
method in, so -0 for the deprecation.
>
>>>> * Shouldn't the "cumulativeProbability(double x0, double x1)"
>>>> method be
>>>>    renamed "probability(double x0, double x1)"?
>>
>> Does everyone agree to deprecate this method (in 3.1) and remove
>> and replace
>> it (in 4.0) with a method named "probability(double x0, double x1)"?
>
> I would prefer to:
>  - add new method (3.1)
>  - deprecate old method (3.1)
>  - move impl to new method (3.1)
>  - redirect old method to new method (3.1)
>  - remove old method (4.0)
>
> That way, we can now change our code to use the new method, and
> not get any deprecation warnings on use of the old deprecated
> method, for which no alternative exists...

Sounds like a reasonable approach and +1 for the rename.

Phil
>
>>
>> Regards,
>> Gilles
>>
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>
> Dennis
>
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>


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