[SciPy-User] poisson distribution in scipy.stats

Robert Kern robert.kern@gmail....
Mon Nov 9 15:25:24 CST 2009


On Mon, Nov 9, 2009 at 15:21, Davide Cittaro
<davide.cittaro@ifom-ieo-campus.it> wrote:
>
> On Nov 9, 2009, at 10:03 PM, scipy-user-request@scipy.org wrote:
>
> Message: 5
> Date: Mon, 9 Nov 2009 15:00:29 -0600
> From: Robert Kern <robert.kern@gmail.com>
> Subject: Re: [SciPy-User] poisson distribution in scipy.stats
> To: SciPy Users List <scipy-user@scipy.org>
> Message-ID:
> <3d375d730911091300h6d9b4df6u4be1e6ae0811b12@mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> On Mon, Nov 9, 2009 at 14:58, Davide Cittaro
> <davide.cittaro@ifom-ieo-campus.it> wrote:
>
> Hi all,
>
> about the poisson generator... given l (expected) and k (found) I guess that
>
> the way to get the probability of k I have to do this:
>
> d = scipy.stats.poisson(l)
>
> p = pmf(k)
>
> Correct.
>
> which I found being the same of
>
> p = scipy.stats.poisson.pmf(l, k)
>
> Also correct.
>
>
> Although I've just plotted values and they are sligthly different... the
> second version does have only a max value at l, whereas the first has two
> maxima (l and l-1)

I'm sorry. I meant "Wrong."

p = scipy.stats.poisson.pmf(k, l)

> I've here some code in which it is written:
>
> d = scipy.stats.poisson(l, k)
>
> That one is completely wrong.
>
>
> Ok, I see... It looks like it shifts the pmf of k... but how does it works?
> I mean, how the discrete distribution constructor interprets this kind of
> declaration?

Exactly as the documentation states:

    myrv = poisson(mu,loc=0)
        - frozen RV object with the same methods but holding the given
shape and location fixed.

-- 
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


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