[Numpy-discussion] Strange behavior of np.sinc

Robert Kern robert.kern@gmail....
Sat Jun 26 23:39:58 CDT 2010


On Sat, Jun 26, 2010 at 23:33, David Goldsmith <d.l.goldsmith@gmail.com> wrote:
> Hi!  The docstring for numpy.lib.function_base.sinc indicates that the
> parameter has to be an ndarray, and that it will return the limiting value 1
> for sinc(0).  Checking to see if it should actually say array_like, I found
> the following (Python 2.6):
>
>>>> np.sinc(np.array((0,0.5)))
> array([ 1.        ,  0.63661977])
>>>> np.sinc((0,0.5))
> array([        NaN,  0.63661977])
>>>> np.sinc([0,0.5])
> array([        NaN,  0.63661977])
>>>> np.version.version
> '1.4.1'
>
> So, it doesn't choke on non-array sequences, and appears to return values
> consistent w/ array input, except at 0.  Bug in code (failure at 0 if in a
> sequence) and in the doc (ndarray should be array_like)?

Bug in both code and docs. There should be an "x = np.asanyarray(x)"
before the rest of the code.

-- 
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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