[SciPy-Dev] scipy.stats

josef.pktd@gmai... josef.pktd@gmai...
Sun Apr 22 12:38:11 CDT 2012


On Sun, Apr 22, 2012 at 1:28 PM, nicky van foreest <vanforeest@gmail.com> wrote:
> On 22 April 2012 02:41,  <josef.pktd@gmail.com> wrote:
>> On Sat, Apr 21, 2012 at 5:58 PM, nicky van foreest <vanforeest@gmail.com> wrote:
>>> On 21 April 2012 23:45,  <josef.pktd@gmail.com> wrote:
>>>> On Sat, Apr 21, 2012 at 5:31 PM, nicky van foreest <vanforeest@gmail.com> wrote:
>>>>>> In [11]: from scipy.stats import uniform
>>>>>>
>>>>>> In [12]: U = uniform(loc = 3, scale = 5)
>>>>>>
>>>>>> In [13]: U.mean()
>>>>>> Out[13]: 5.5
>>>>>>
>>>>>> In [14]: U.moment(1)
>>>>>> Out[14]: 0.5
>>>>>
>>>>> Might this problem be due to the fact that my ubuntu machine does not
>>>>> support the latest version of scipy.stats?
>>>>
>>>> I'm stil on 0.9 and there is no loc, scale option
>>>>
>>>>>>> import scipy
>>>>>>> scipy.__version__
>>>> '0.9.0'
>>>>>>> stats.uniform.moment(loc = 3, scale = 5)
>>>> Traceback (most recent call last):
>>>>  File "<stdin>", line 1, in <module>
>>>> TypeError: moment() got an unexpected keyword argument 'loc'
>>>>>>> U.moment(1)
>>>> 0.5
>>>>>>> stats.uniform.moment(1)
>>>> 0.5
>>>>
>>>> Obviously I'm not up to date in this.
>>>>
>>>> can you try the distribution directly instead of the frozen distribution?
>>>
>>> I am having the same problems as you, although:
>>>
>>> In [9]: ? uniform.moment
>>> Type:           instancemethod
>>> Base Class:     <type 'instancemethod'>
>>> String Form:    <bound method uniform_gen.moment of
>>> <scipy.stats.distributions.uniform_gen object at 0x2e901d0>>
>>> Namespace:      Interactive
>>> File:           /usr/lib/python2.7/dist-packages/scipy/stats/distributions.py
>>> Definition:     uniform.moment(self, n, *args)
>>> Docstring:
>>>    n'th order non-central moment of distribution
>>>
>>>    Parameters
>>>    ----------
>>>    n: int, n>=1
>>>        order of moment
>>>
>>>    arg1, arg2, arg3,... : array-like
>>>        The shape parameter(s) for the distribution (see docstring of the
>>>        instance object for more information)
>>
>>>>> stats.uniform.moment(1, loc=3, scale=1)
>> 3.5
>>>>> stats.uniform(loc=3, scale=1).moment(1)
>> 3.5
>>
>>>>> import scipy
>>>>> scipy.__version__
>> '0.10.0b2'
>>
>>
>> version mismatch with new documentation
>>
>> In the older versions of scipy, the frozen distributions didn't always
>> pass on the keywords, loc and scale, so they were just quietly
>> ignored.
>>
>> It looks like now moment handles loc and scale
>>
>>>>> stats.uniform.mean(1, loc=3, scale=5)
>> 5.5
>>>>> stats.uniform.moment(1, loc=3, scale=5)
>> 5.5
>>
>>>>> stats.uniform.ppf([0, 1], loc=3, scale=5)
>> array([ 3.,  8.])
>>>>> stats.uniform.ppf([0, 1], loc=3, scale=5).mean()
>> 5.5
>>
>>
>> Josef
>
> Ok. So this is clear now. . Let's try to wrap up the above couple of
> mails. The problem with the moments is solved. The point about
> rv.dist.b in the examples text is not in my opinion. Is it ok to make
> a ticket for this? I'll try to figure out how to do this. Hopefully
> this is covered in the doc of Ralf.

Fine, the template would need a new place holder, the value can then
be inserted when the doc string is created in the line that I linked
to, I think.

>
> BTW. I can also try to repair a few of the tickets. For instance, I
> came across a similar problem like the one in
> http://projects.scipy.org/scipy/ticket/1493. I think I have a nice
> solution for this.

That would be a good ticket to have a solution for.

Thanks,

Josef

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