GNU Scientific Library - Bugs: bug #43326, Bug in gsl_ran_poisson_pdf() for...
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bug #43326: Bug in gsl_ran_poisson_pdf() for mu = 0.0
Submitter: | Patrick Alken <psa> | ||
Submitted: | Mon 29 Sep 2014 05:42:30 PM UTC | ||
Category: | Runtime error | Severity: | 3 - Normal |
Operating System: | Status: | None | |
Assigned to: | None | Open/Closed: | Open |
Release: |
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From kai =dot= wassmuss =at= gmx =dot= de
Dear GSL maintainers,
gsl_ran_poisson_pdf() uses a clever method to evaluate the poisson pmf
p(n) = (mu^n / n!) exp(-mu)
without evaluating the factorial directly.
To do so, it evaluates log(mu). In the special case mu = 0 this returns
-nan and so gsl_ran_poisson_pdf() returns -nan.
mu = 0 corresponds to a poisson process with rate 0 and the return value
of gsl_ran_poisson_pdf(k, mu) should consequently be 1.0 for k=0 and 0.0
for k>0.
This bug is similar to
https://savannah.gnu.org/bugs/?func=detailitem&item_id=36328, which was
accepted for octave.
Best regards,
Kai