[Numpy-discussion] What should be the value of nansum of nan's?

Charles R Harris charlesr.harris@gmail....
Mon Apr 26 12:03:38 CDT 2010


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<http://projects.scipy.org/numpy/ticket/1123#comment:11>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

Chuck
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