[Numpy-discussion] Testing for close to zero?

Robert Kern robert.kern@gmail....
Mon Jan 19 22:17:02 CST 2009

On Mon, Jan 19, 2009 at 22:09, Charles R Harris
<charlesr.harris@gmail.com> wrote:
> On Mon, Jan 19, 2009 at 7:23 PM, Jonathan Taylor
> <jonathan.taylor@utoronto.ca> wrote:
>> Interesting.  That makes sense and I suppose that also explains why
>> there is no function to do this sort of thing for you.
> A combination of relative and absolute errors is another common solution,
> i.e., test against relerr*max(abs(array_of_inputs)) + abserr. In cases like
> this relerr is typically eps and abserr tends to be something like 1e-12,
> which keeps you from descending towards zero any further than you need to.

I don't think the absolute error term is appropriate in this case. If
all of my inputs are of the size 1e-12, I would expect a result of
1e-14 to be significantly far from 0.

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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