Looking for triangulator/interpolator

Travis E. Oliphant oliphant.travis at ieee.org
Sat May 27 09:22:15 CEST 2006


Grant Edwards wrote:
> On 2006-05-27, Travis E. Oliphant <oliphant.travis at ieee.org> wrote:
> 
>>> I need to interpolate an irregularly spaced set of sampled
>>> points: Given a set of x,y,z points, I need to interpolate z
>>> values for a much finer x,y grid.
>> How many x,y,z points do you have?
> 
> I've got about 700 data points.  They're arranged irregularly
> along arcs arranged in sort of truncated fan-shape.
> 
>> Did you try the fitpack function bisplrep in scipy?
> 
> Not recently.  I spent a month or so wrestling with bisplrep a
> while back, but was unable to get stable results (either with
> real world data or with the example from the tutorial):
> 
> http://www.visi.com/~grante/scipy/interpolate.html
> http://www.scipy.net/pipermail/scipy-user/2004-December/003921.html
> 
> I switched to a trianguation scheme shortly after that posting,
> and haven't tired bisplrep since then.
> 

Not that you made a bad choice.  I do wonder, how much of your 
difficulty was with the interface to the underlying fitpack routines. 
The interface is pretty involved as there are lots of parameter choices 
to the underlying routine.  It's very possible the interface is broken 
in some strange way.

Given how many people want to do interpolation.  I'm surprised nobody 
has looked into fixing up the fitpack routines that do it.  I suppose 
it's possible that the underlying fitpack routines are faulty in 2-d.

Your examples will help in that study.

Pearu made some nice class-based interfaces to fitpack in 2003.  They 
are in SciPy, but, it appears that people aren't making much use of 
them.  Did you try them?

They are in fitpack2.py

There are new wrappers for it





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