[SciPy-user] scipy.stats.percentileofscore : something strange

Samuel GARCIA sgarcia@olfac.univ-lyon1...
Thu Dec 13 04:36:15 CST 2007



Matthieu Brucher a écrit :
>
>
> 2007/12/13, Samuel GARCIA <sgarcia@olfac.univ-lyon1.fr 
> <mailto:sgarcia@olfac.univ-lyon1.fr>>:
>
>     Hi all,
>     I found something strange in scipy.stats.percentileofscore
>
>     In [1]: from scipy import *
>
>     In [2]: a = rand(10000)
>
>     In [3]: stats.percentileofscore(a,.2)
>     Out[3]: 20.0157565073
>              This OK.
>
>
>     In [4]: stats.percentileofscore(a,.0002)
>     Out[4]: 102.898311442
>                 This is strange !!!!!
>
>
> This may be a bug
>  
>
>     In [5]: stats.percentileofscore(a,1.4)
>     ---------------------------------------------------------------------------
>     <type 'exceptions.IndexError
>     '>            Traceback (most recent call last)
>
>     //home/sgarcia//<ipython console> in <module>()
>
>     /usr/lib/python2.5/site-packages/scipy/stats/stats.py in
>     percentileofscore(a, score, histbins, defaultlimits)
>         942     cumhist = np.cumsum(h*1, axis=0)
>         943     i = int((score - lrl)/float(binsize))
>
>     --> 944     pct =
>     (cumhist[i-1]+((score-(lrl+binsize*i))/float(binsize))*h[i])/float(len(a))
>     * 100
>         945     return pct
>         946
>
>     <type 'exceptions.IndexError'>: index out of bounds
>
>                    This does not work...
>
>
> I expect this to raise this exception, you cannot take a percentile 
> outside [0, 1] (1.4 = 140%)

I think that it should return 100 if superior to rigtht limit and 0 if 
inferior to left limit.
No ?


>
> Matthieu
> -- 
> French PhD student
> Website : http://matthieu-brucher.developpez.com/
> Blogs : http://matt.eifelle.com and http://blog.developpez.com/?blog=92
> LinkedIn : http://www.linkedin.com/in/matthieubrucher
> ------------------------------------------------------------------------
>
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-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Samuel Garcia
Laboratoire de Neurosciences Sensorielles, Comportement, Cognition.
CNRS - UMR5020 - Universite Claude Bernard LYON 1
Equipe logistique et technique
50, avenue Tony Garnier
69366 LYON Cedex 07
FRANCE
Tél : 04 37 28 74 64
Fax : 04 37 28 76 01
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