[SciPy-dev] new function regrid for fitpack2

John Travers jtravs at gmail.com
Thu Oct 12 11:35:36 CDT 2006


I started to look at this and think some extra work is required.

The problem is that regrid requires the data to be evenly spaced on a
rectangular grid, rather than just a rectangular grid (which could
have, say, increasing spacing in the y direction). I think this may
limit its use more than users of interp2d would expect.

The problem then is:

1. The currently used function (dierckx surfit) is not suitable for
interpolation and needs to be replaced (it segfaults my simple test).

2. regrid works very well (fast, low mem etc.) for regular rectangular
grids, but can't handle varying rectangular grids, let alone scattered
data.

3. uses probably expect that at least varying rectangular grids are handled

Solutions:

a) just use regrid and say we can't work with no regular data.

b) use a regridding method to get regular data if required, then use regrid

I favour the second. As it happens, this is what MATLAB does which I
guess is a reasonable example to follow. The are several regridding
methods. MATLAB uses the freely available (I think scipy compatible)
Qhull code.

So I'll have a look at packaging the qhull code into scipy, then we
can move on from there.

In the mean time, do we use regrid over the restricted domain, or use
the current surfit (which only works in very few cases).

Regards,
John


On 12/10/06, Stefan van der Walt <stefan at sun.ac.za> wrote:
> On Thu, Oct 12, 2006 at 01:42:44PM +0100, John Travers wrote:
> > Thanks! Sorry for the long lines, I'll be stricter on the format next
> > time. I can send a patch for interp2d this evening (London time) if
> > you want.
>
> That's great, I'll keep an eye out for it.  If anyone on the list
> currently uses interp2d on irregularly gridded data, now is the time
> to speak up.
>
> Cheers
> Stéfan
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>


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