[SciPy-dev] stats.distributions.poisson loc parameter : is it wise ?

Robert Kern robert.kern@gmail....
Thu Aug 6 17:21:49 CDT 2009


On Thu, Aug 6, 2009 at 17:02, Pierre GM<pgmdevlist@gmail.com> wrote:
>
> On Aug 6, 2009, at 5:49 PM, Robert Kern wrote:
>
>> On Thu, Aug 6, 2009 at 16:43, Pierre GM<pgmdevlist@gmail.com> wrote:
>>> Even if
>>> the scale is simply discarded already, using a location will probably
>>> NOT give the expected result
>>
>> It depends on what your expectations are. For the discrete
>> distributions, all the loc parameter means is this, as documented:
>>
>>  pmf(x; loc) -> pmf(x-loc)
>>
>> That's it. I don't know why you would expect anything else.
>
> Because using a location parameter, you change the support domain.

It should be noted that the location parameter changes the support
domain *as a consequence* of the above transformation. Changing the
support domain (and holding everything else fixed) is not the defining
characteristic of the location parameter.

-- 
Robert Kern

"I have come to believe that the whole world is an enigma, a harmless
enigma that is made terrible by our own mad attempt to interpret it as
though it had an underlying truth."
  -- Umberto Eco


More information about the Scipy-dev mailing list