Re: Interpol. irregular grid to irregular grid

["Mark Hadfield" <m.hadfield(at)niwa.cri.nz>]

<deja_jlin@my-deja.com> wrote in message 95nn6i$25g$1@nnrp1.deja.com">news:95nn6i$25g$1@nnrp1.deja.com...
> howdy!
>
> i'm trying to interpolate data from one irregular
> 2-D grid to another (different) irregular 2-D
> grid:
>
> - does IDL have any other built-in functions
> besides MIN_CURVE_SURF that can do this?

Not that I'm aware of. It's a pity because there's no fundamental reason why
TRIGRID (for example) couldn't be modified to handled irregular output
grids.

> - does anyone have any warnings regarding the
> behavior of MIN_CURVE_SURF?

Yes! It's terribly slow when the input grid is of a significant size. For an
NxN input grid, the execution time of MIN_CURVE_SURF increases as approx.
N^3. This is because the alogorithm is non-local, i.e. every point in the
input grid affects every point in the output grid.

> - has anyone implemented irregular-to-irregular
> interpolations using other algorithms?

No but you could try calling TRIGRID repeatedly, once for every output
point...

---
Mark Hadfield
m.hadfield@niwa.cri.nz  http://katipo.niwa.cri.nz/~hadfield
National Institute for Water and Atmospheric Research