Re: [Bug-gsl] [bug #42502] wrong results of the function gsl_cdf_ugaussian_Pinv

[Peter Johansson]

On 06/04/2014 04:51 AM, Patrick Alken wrote:
> URL:
>    <http://savannah.gnu.org/bugs/?42502>
>
>                   Summary: wrong results of the function gsl_cdf_ugaussian_Pinv
>                   Project: GNU Scientific Library
>              Submitted by: psa
>              Submitted on: Tue 03 Jun 2014 06:51:52 PM GMT
>                  Category: Runtime error
>                  Severity: 3 - Normal
>          Operating System:
>                    Status: None
>               Assigned to: None
>               Open/Closed: Open
>                   Release:
>           Discussion Lock: Any
>
>      _______________________________________________________
>
> Details:
>
> #include<gsl/gsl_math.h>
> #include<stdio.h>
>
> int main(){
>      double x= 0.5;
>      double res = gsl_cdf_ugaussian_Pinv(x);
>      printf("icdf(%f)=%f\n",x,res);
>      return 0;
> }

This code does not compile because gsl_cdf.h is not #included.

> For some reason the output is: *icdf(0.500000)=1.000000*
>
> Which is wrong, it should be: *icdf(0.500000)=0.000000 (because P(X<0)=0.5)*

gsl_cdf_ugaussian_Pinv(0.5) returns 0.0 with gsl 1.15.

Cheers,


--
Peter Johansson
http://dev.thep.lu.se/yat