[Numpy-discussion] What should be the value of nansum of nan's?
Travis Oliphant
oliphant@enthought....
Wed Apr 28 11:15:41 CDT 2010
On Apr 26, 2010, at 12:03 PM, Charles R Harris wrote:
>
>
> On Mon, Apr 26, 2010 at 10:55 AM, Charles R Harris <charlesr.harris@gmail.com
> > wrote:
> Hi All,
>
> We need to make a decision for ticket #1123 regarding what nansum
> should return when all values are nan. At some earlier point it was
> zero, but currently it is nan, in fact it is nan whatever the
> operation is. That is consistent, simple and serves to mark the
> array or axis as containing all nans. I would like to close the
> ticket and am a bit inclined to go with the current behaviour
> although there is an argument to be made for returning 0 for the
> nansum case. Thoughts?
>
>
> To add a bit of context, one could argue that the results should be
> consistent with the equivalent operations on empty arrays and always
> be non-nan.
>
> In [1]: nansum([])
> Out[1]: nan
>
> In [2]: sum([])
> Out[2]: 0.0
I favor nansum([]) returning 0.0 which implies returning 0.0 when all
the elements are nan.
-Travis
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