[SciPy-Dev] RBF epsilon (changes 0.15 => 0.16)

[Ariel Rokem]

Hi Evgeni - thanks for the feedback!

On Fri, Aug 28, 2015 at 11:33 AM, Evgeni Burovski <
evgeny.burovskiy at gmail.com> wrote:

> Hi Ariel,
>
> Off-the-cuff, I'd think that the value of epsilon is best managed on
> the user side.
> [I can't say anything intelligent about the issue in dipy, so I'd
> rather say nothing about it].
>

That was my intuition. Just wanted to make sure we're not doing anything
crazy.

In general, it seems that scipy's rbf implementation could use some
> work, and here's one issue which summarizes some suggestions for it:
>
> https://github.com/scipy/scipy/issues/4790
>
> There is also a PR,
>
> https://github.com/scipy/scipy/pull/5070
>
> which was closed by the author, and I'm not sure what's the status of it.
>
> As things stand, chances are that we'll be tempted to break backwards
> compat for scipy.interpolate.Rbf. Since you're using it, your
> suggestions are most welcome (and patches are even more so!)
>
> OK - I will read up on this topic (I see there are some suggestions on
that issue), and try to see whether I can be helpful.

Thanks again,

Ariel


> Cheers,
>
> Evgeni
>
>
>
> On Thu, Aug 27, 2015 at 1:11 AM, Ariel Rokem <arokem at gmail.com> wrote:
> > Hi everyone,
> >
> > In our work on dipy, we've run into a small issue moving from 0.15 to
> 0.16:
> >
> > https://github.com/nipy/dipy/issues/688
> >
> > The gist of this is that we are using RBF to interpolate a signal
> measured
> > on the unit sphere. To do this, we have designed a custom 'norm' function
> > based on the angle between measurements (rather than the default
> Euclidean).
> > Code is here:
> >
> > https://github.com/nipy/dipy/blob/master/dipy/core/sphere.py#L500
> >
> > This seemed to work fine with 0.15, but the changes to the default
> epsilon
> > introduced here: https://github.com/scipy/scipy/pull/4643 seem to be
> > throwing us off.
> >
> > I've taken a look at the discussion on that PR and the issue that led to
> > this work, and it does make sense, but I wanted to get some feedback to
> see
> > how we should proceed. Setting a larger default epsilon in our code
> > (effectively undoing this change) would be one way to go, but I want to
> make
> > sure that it wouldn't be an obvious blunder, and that there isn't some
> issue
> > on scipy that we should be thinking about.
> >
> > Thanks!
> >
> > Ariel
> >
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> > SciPy-Dev at scipy.org
> > http://mail.scipy.org/mailman/listinfo/scipy-dev
> >
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