[Scipy-tickets] [SciPy] #299: gammaincinv gives incorrect answers

SciPy scipy-tickets@scipy....
Fri Nov 2 02:02:38 CDT 2007


#299: gammaincinv gives incorrect answers
---------------------------+------------------------------------------------
 Reporter:  djcmackay      |        Owner:  cookedm 
     Type:  defect         |       Status:  assigned
 Priority:  normal         |    Milestone:  0.7     
Component:  scipy.special  |      Version:          
 Severity:  normal         |   Resolution:          
 Keywords:  gammainc       |  
---------------------------+------------------------------------------------
Changes (by cookedm):

  * status:  new => assigned
  * owner:  somebody => cookedm

Old description:

> For extreme values, gamaincinv gives the answer '0.0'
> when it should not do so.
> Examples:
>
> >>> import scipy.special as S
> >>> S.gammainc( 50 , 12.00 )
> 2.3998794536786009e-16
> >>> S.gammaincinv( 50 , 2.39e-16 )
> 11.996909478523992
> >>> S.gammainc( 50 , 11.00 )
> 8.2075477738848345e-18
> >>> S.gammaincinv( 50 , 8e-18 )
> 0.0
>

> Python 2.4.3 (#2, Oct  6 2006, 07:52:30)
> [GCC 4.0.3 (Ubuntu 4.0.3-1ubuntu5)] on linux2
>
> David
> mackay@mrao.cam.ac.uk

New description:

 For extreme values, gamaincinv gives the answer '0.0'
 when it should not do so.
 Examples:

 {{{
 >>> import scipy.special as S
 >>> S.gammainc( 50 , 12.00 )
 2.3998794536786009e-16
 >>> S.gammaincinv( 50 , 2.39e-16 )
 11.996909478523992
 >>> S.gammainc( 50 , 11.00 )
 8.2075477738848345e-18
 >>> S.gammaincinv( 50 , 8e-18 )
 0.0
 }}}

 Python 2.4.3 (!#2, Oct  6 2006, 07:52:30)
 [GCC 4.0.3 (Ubuntu 4.0.3-1ubuntu5)] on linux2

 David
 mackay@mrao.cam.ac.uk

-- 
Ticket URL: <http://scipy.org/scipy/scipy/ticket/299#comment:2>
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