[Numpy-discussion] bug in stats.binom? Or is it just me.

David Huard david.huard at gmail.com
Tue Jul 11 21:36:09 CDT 2006


There probably is a bug because
stats.binom.ppf(.975, 100, .5) crashes the ipython shell.
win2k,  P3,  latest binary release.

David

2006/7/11, JJ <josh8912 at yahoo.com>:
>
> Am I using the wrong syntax for the binom.ppf command, or is there a bug?
>
> >>> stats.binom.ppf(.975,100,.5)
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
>   File "/usr/lib64/python2.4/site-packages/scipy/stats/distributions.py",
> line
> 3590, in ppf
>     insert(output,cond,self._ppf(*goodargs) + loc)
>   File "/usr/lib64/python2.4/site-packages/numpy/lib/function_base.py",
> line
> 501, in insert
>     return _insert(arr, mask, vals)
> TypeError: array cannot be safely cast to required type
> >>>
> -----------------
> The info pages for binom.ppf state that:
> binom.ppf(q,n,pr,loc=0)
>         - percent point function (inverse of cdf --- percentiles)
> So I would expect binom.ppf to take three variables.
>
> I expected the function to return a number, such as is done in matlab:
> N = 100
> alpha = 0.05
> p1 = 0.30
> cutoff = binoinv(1-alpha, N, p1)
>
> cutoff =
>
>     38
> Any suggestions?
>
>
> JJ
>
>
>
>
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