[Scipy-tickets] [SciPy] #583: negative binomial fails with 0 < r < 1
SciPy
scipy-tickets@scipy....
Fri Jan 11 16:31:27 CST 2008
#583: negative binomial fails with 0 < r < 1
-------------------------+--------------------------------------------------
Reporter: danhs | Owner: somebody
Type: defect | Status: new
Priority: normal | Milestone:
Component: scipy.stats | Version: none
Severity: normal | Keywords: nbinom, negative binomial
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With r < 1 it seems that the negative binomial function has some
noteworthy failures.
Example:
{{{
nbinom = scipy.stats.nbinom(0.88, 0.42)
# These will have errors:
nbinom.rvs()
nbinom.cdf()
nbinom.ppf()
# Strangely this does not:
nbinom.isf()
}}}
My purpose was to create a random sample from the negative binomial so, I
was able to use the following code successfully:
{{{
nbinom.isf(random.random())
}}}
Negative binomial is defined for r greater than 0 (real numbers), and for
p in range 0 to 1 according to wikipedia
So these should be acceptable inputs.
This was observed on scipy 0.6.0.
--
Ticket URL: <http://www.scipy.org/scipy/scipy/ticket/583>
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