[SciPy-Dev] SciPy-Dev Digest, Vol 92, Issue 8

Charles R Harris charlesr.harris@gmail....
Fri Jun 10 22:36:22 CDT 2011


On Fri, Jun 10, 2011 at 7:04 PM, Ole Nielsen
<ole.moller.nielsen@gmail.com>wrote:

> Thank you everyone for your suggestions. I didn't realise that
> RectBivariateSpline is a global method, but now it makes sense what I see in
> terms of ringing and handling of NaN.
>
> I am really interested in the local methods suggested by Chuck (bi-cubic
> interpolation or bilinear. However, looking in scipy.ndimage I couldn't find
> this kind of thing. Looking at GDAL this seems to be available only for
> resampling.
> I couldn't find LinearNDInterpolator either. Can anyone tell me where to
> find these packages please.
>
> Just to recab, what we need is a local bilinear interpolation from regular
> grid data to a collection of points which handles NaN in a sensible way.
>

Well, I looked a bit more closely at the ndimage interpolation routines and
they are all spline based, so that leaves you with splines of order 1 as the
only option there, which I think is equivalent to bilinear. The
LinearNDInterpolator uses triangulation and will give a linear
interpolation, but such depends on the triangulation. It's a shame that the
offerings are so sparse, matplotlib's imshow has a lot more options.
Scikits.image doesn't seem to concern itself with interpolation (yet), so I
don't know where else you can look. Can you be a bit more specific about the
grid and how you want to resample it? That is, do you need to sample it a
random points, or just resample it on a different grid, etc.

<snip>

Chuck
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