[Numpy-discussion] What should be the return type of average?

Sebastian Haase haase@msg.ucsf....
Sun Mar 16 05:11:39 CDT 2008


On Sun, Mar 16, 2008 at 1:08 AM, Charles R Harris
<charlesr.harris@gmail.com> wrote:
> Hi,
>
> I want to fix up the average function. I note that the return dtype is not
> specified, nor is the precision of the accumulator. Both of these can be
> specified for the mean method and I wonder what should be the case for
> average. Or should we just use double precision? That would seem appropriate
> to me most of the time, but wouldn't match what happens with mean and would
> lose precision in the case of extended precision doubles. There is also no
> out keyword, do we want one?
>

Hi,
I'm starting to forget... but faintly I'm remembering that there might
have been some extended discussion about this on this list.
We work with large multi-dimensional image data, so if, for example, I
have n (small) 50x512x512 3D-images that I want to average into one
50x512x512 image, the most memory I can afford is single precession
float32. (Also the original dynamic range is 16bit at best anyway)

I was just checking my archives:
http://projects.scipy.org/scipy/numpy/ticket/465#comment:2 (by
oliphant) actually already says this.

Furthermore, an "out" variable  like it is in most functions in the
ndimage module would certainly be good to have.

Cheers,
Sebastian Haase


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