[SciPy-user] problems with stats
danny shevitz
danny_shevitz at yahoo.com
Tue Apr 27 13:43:03 EDT 2004
Howdy,
I've encountered two problems with the binomial distribution in the
stats module. The first is trivial and I believe just an argument
checking problem.
>>> binom.pdf(0,3,.5)
bdtr domain error
1.#QNAN
(the answer should be .125 of course)
The second is a little more significant. I'm trying to invert the
binomial distribution using ppf. I looked at distributions.py
class binom_gen(rv_discrete):
.
.
.
def _ppf(self, q, n, pr):
vals = ceil(special.bdtrik(q,n,pr))
vals1 = vals-1
temp = special.bdtr(vals1,n,pr)
return where(temp >= q, vals1, vals)
and ppf is in fact implemented, but when I try to run it I get an
error.
>>> binom.ppf(3,4,.95)
Traceback (most recent call last):
File "<stdin>", line 1, in ?
File ".\site-packages\scipy\stats\distributions.py", line 2371, in
ppf
TypeError: _ppf() takes exactly 4 arguments (3 given)
Does anyone know what's going on. Am I misusing something?
thanks,
Danny
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