[SciPy-dev] bug in scipy.stats package

[Leon Adams]

Thanks for the update. Currently I am running scipy 0.7.1 (from python XY
distribution) on vista and version 0.7.0-2 on ubuntu with both exhibiting
this
behavior. I will look into upgrading.

Thanks again


On Fri, Jan 8, 2010 at 12:40 PM, <josef.pktd@gmail.com> wrote:

> On Fri, Jan 8, 2010 at 11:56 AM, Leon Adams <skorpio11@gmail.com> wrote:
> >
> > Hi all,
> > I am currently doing some work involving distribution fitting and it
> looks
> > like a came across a strange bug in the ppf function of the gamma
> > distribution. Can some one else verify and if so suggest possible
> > resolution. Below is a sample of my python script:
> >
> > import scipy.stats as st
> > import numpy as np
> > nbins = 12
> > binProb = np.zeros(nbins) + 1.0/nbins
> > binSumProb = np.add.accumulate(binProb)
> > print binSumProb
> > print st.gamma.ppf(binSumProb,0.6379,loc=1.6,scale=39.555)
> >
> > With the following output:
> > [ 0.08333333  0.16666667  0.25        0.33333333  0.41666667  0.5
> >   0.58333333  0.66666667  0.75        0.83333333  0.91666667  1.        ]
> > [  2.28713122   3.68072087   1.6          8.20183111  11.42062087
> >   15.44977132  20.5371578   27.11627185  36.01838095  49.13633397
> >   72.58240868          Inf]
>
> My result look correct, see below. Which version of scipy are you using?
> I think this was http://projects.scipy.org/scipy/ticket/975
> which would mean the fix is only in trunk
>
> Thanks for reporting it
>
> Josef
>
>
> >>> scipy.version.version
> '0.8.0.dev6156'
>
> >>> import scipy.stats as stats
> >>> import numpy as np
> >>> nbins = 12
> >>> binProb = np.zeros(nbins) + 1.0/nbins
> >>> binSumProb = np.add.accumulate(binProb)
> >>> print binSumProb
> [ 0.08333333  0.16666667  0.25        0.33333333  0.41666667  0.5
>  0.58333333  0.66666667  0.75        0.83333333  0.91666667  1.        ]
> >>> print stats.gamma.ppf(binSumProb,0.6379,loc=1.6,scale=39.555)
> [  2.28713122   3.68072087   5.64774079   8.20183111  11.42062087
>   15.44977132  20.5371578   27.11627185  36.01838095  49.13633397
>  72.58240868          Inf]
>
>
> >
> > The problem occurs at an input value of 0.25, the ppf returns the
> location
> > parameter (in this case 1.6)
> >
> > Thanks in advance
> > --
> > Leon Adams
> >
> > _______________________________________________
> > SciPy-Dev mailing list
> > SciPy-Dev@scipy.org
> > http://mail.scipy.org/mailman/listinfo/scipy-dev
> >
> >
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-- 
Leon Adams
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