[Numpy-discussion] random.uniform documentation bug?
David Goldsmith
d.l.goldsmith@gmail....
Tue Feb 23 15:44:32 CST 2010
OK, fixed in Wiki. (& "OK to apply" set to "Yes")
DG
On Tue, Feb 23, 2010 at 10:29 AM, Robert Kern <robert.kern@gmail.com> wrote:
> On Tue, Feb 23, 2010 at 08:21, Alan G Isaac <aisaac@american.edu> wrote:
> > This behavior does not match the current documentation.
> >
> >>>> np.random.uniform(low=0.5,high=0.5)
> > 0.5
> >>>> np.random.uniform(low=0.5,high=0.4)
> > 0.48796883601707464
> >
> > I assume this behavior is intentional and it is
> > the documentation that is in error (for the case
> > when high<=low)?
>
> Well, the documentation just doesn't really address high<=low. In any
> case, the claim that the results are in [low, high) is wrong thanks to
> floating point arithmetic. It has exactly the same issues as the
> standard library's random.uniform() and should be updated to reflect
> that fact:
>
>
> random.uniform(a, b)
> Return a random floating point number N such that a <= N <= b for a
> <= b and b <= N <= a for b < a.
>
> The end-point value b may or may not be included in the range
> depending on floating-point rounding in the equation a + (b-a) *
> random().
>
>
> We should address the high < low case in the documentation because
> we're not going to bother raising an exception when high < low.
>
> --
> Robert Kern
>
> "I have come to believe that the whole world is an enigma, a harmless
> enigma that is made terrible by our own mad attempt to interpret it as
> though it had an underlying truth."
> -- Umberto Eco
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