I finally got around to add the tests. Updates pushed to github now.
(Here<http://www.gnu.org/software/gsl/manual/html_node/Factorials.html>says
that GSL_SF_FACT_NMAX is 170 instead of 100).

Best,
Maggie


On Wed, Oct 31, 2012 at 4:14 PM, Maggie X <[email protected]> wrote:

> Got it. I'll see if I can get it in. Thanks!
>
>
> On Wed, Oct 31, 2012 at 3:42 PM, David Mertens 
> <[email protected]>wrote:
>
>> I can work on some tests in a few days, though I'm busy at the moment.
>>
>> There should be two tests: one set that  tests would be compare the
>> results of the factorial form and the Stirling form where they are in good
>> numerical agreement, basically for 50 < x < 100, and ensure that they agree
>> within bit noise (by one measure or another).
>>
>> The second set of tests are to ensure that the code for the combined form
>> (called pmf_poisson) gives results that are *identical* to those of the
>> factorial form for x < 50, and the Stirling form for x > 100.
>>
>> David
>>
>>
>>
>> On Wed, Oct 31, 2012 at 2:28 PM, Maggie X <[email protected]> wrote:
>>
>>> Thanks for the update, David! Would you mind adding a couple test cases?
>>> I'd be happy to add it too if you can suggest some numbers to test.
>>>
>>> Best,
>>> Maggie
>>>
>>> On Wed, Oct 31, 2012 at 12:38 PM, David Mertens <
>>> [email protected]> wrote:
>>>
>>>> Maggie (and other Stats PDLers) -
>>>>
>>>> I ran into some numerical stability issues with the Poisson probability
>>>> mass function. The Poisson distribution is mathematically well-behaved, but
>>>> is not numerically stable. Fortunately, I was able to use Stirling's
>>>> approximation to increase the range of accuracy and the allowed input range
>>>> to effectively work for anything.
>>>>
>>>> I've issued a pull request. You can check it out and comment here:
>>>> https://github.com/maggiexyz/PDL-Stats/pull/1
>>>>
>>>> David
>>>>
>>>> P. S. Maggie's recent switch to Github didn't spur my interest in
>>>> PDL::Stats (blame my research for that), but it sure made it a heck of a
>>>> lot easier for me to manage this proposed modification. :-)
>>>>
>>>> --
>>>>  "Debugging is twice as hard as writing the code in the first place.
>>>>   Therefore, if you write the code as cleverly as possible, you are,
>>>>   by definition, not smart enough to debug it." -- Brian Kernighan
>>>>
>>>>
>>>
>>
>>
>> --
>>  "Debugging is twice as hard as writing the code in the first place.
>>   Therefore, if you write the code as cleverly as possible, you are,
>>   by definition, not smart enough to debug it." -- Brian Kernighan
>>
>>
>
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