# [Numpy-discussion] [enhancement] sum_angle() and sum_polar()

Travis Oliphant travis at continuum.io
Mon May 28 14:53:34 EDT 2012

```On May 28, 2012, at 1:02 PM, Ralf Gommers wrote:

>
>
> On Mon, May 28, 2012 at 7:58 PM, Travis Oliphant <travis at continuum.io> wrote:
> I didn't see anyone respond to this, but looking over his simple and elegant solution it seems like a useful addition to the 2-d functions available in NumPy as it works with any 2-d array (image or matrix) and does a transformation on the indices in order to organize the sum.
>
> It is not a general-purpose interpolating approach where the 2-d array is viewed as samples of an underlying continuous function.
>
> Are their other thoughts?
>
> This was discussed (not finished yet) on scipy-dev: http://thread.gmane.org/gmane.comp.python.scientific.devel/16538/focus=16541.
>

That is a useful discussion, but the question about whether this function should just go into NumPy is also of interest.    There are arguments that it could go into NumPy, SciPy, or sckitis-image.   I think going into scikits-image does not make sense because of their general applicability  for more than just images and the fact that in the context of image-processing these functions *just* do nearest neighbor interpolation.

I could see these functions going into scipy.ndimage but again because they are not necessarily just image processing functions, and the fact that they are so simple, perhaps they are best put into NumPy itself.

-Travis

> Ralf
>
>
> -Travis
>
>
>
> On Mar 7, 2012, at 12:39 PM, Robert Jördens wrote:
>
> > Hi everyone,
> > I am proposing to add the the two following functions to
> > numpy/lib/twodim_base.py:
> >
> > sum_angle() computes the sum of a 2-d array along an angled axis
> > sum_polar() computes the sum of a 2-d array along radial lines or
> > along azimuthal circles
> >
> > https://github.com/numpy/numpy/pull/230
> >
> >
> > When I was looking for a solution to these problems of calculating
> > special sums of 2-d arrays I could not find anything and it took me a
> > while to figure out a (hopefully) useful and consistent algorithm.
> > I can see how one would extend these to higher dimensions but that
> > would preclude using bincount() to do the heavy lifting.
> > Looking at some other functions, the doctests might need to be split
> > into real examples and unittests.
> >
> > Best,
> >
> > --
> > Robert Jordens.
> > _______________________________________________
> > NumPy-Discussion mailing list
> > NumPy-Discussion at scipy.org
> > http://mail.scipy.org/mailman/listinfo/numpy-discussion
>
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