Replace interp2d in ProcessedVariable

[rtimms]

We currently use interp2d when creating processed variables, but this is deprecated. We should switch to RegularGridInterpolator.

DeprecationWarning: `interp2d` is deprecated!
`interp2d` is deprecated in SciPy 1.10 and will be removed in SciPy 1.12.0.

For legacy code, nearly bug-for-bug compatible replacements are
`RectBivariateSpline` on regular grids, and `bisplrep`/`bisplev` for
scattered 2D data.

In new code, for regular grids use `RegularGridInterpolator` instead.
For scattered data, prefer `LinearNDInterpolator` or
`CloughTocher2DInterpolator`.

[jeromtom]

2. Alternative to interp2d: regular grid in the transition guide is relevant to this.

[jaskiratsingh2000]

HI @rtimms, and @jeromtom Can you let me know that where can I find the processed variable implementation fo "interp2d"? Thanks! :)

[rtimms]

Here. There may be other places where it appears, so worth searching (e.g. doing ctrl+shift+f in vs code).

[jeromtom]

It can be found here pybamm\solvers\processed_variable.py.

[jeromtom]

Using findstr and running findstr /s /i interp2d *.* gives this

8 mentions of interp2d, the first 4 in the documentation, and the last 4 in the code.

[valentinsulzer]

Sites in sites-packages are not part of documentation, they are installed dependencies.

I don't know what's in your build folder but it looks like it's a duplicate of the repository.

So ignore the first 6, it's only the last two

[jaskiratsingh2000]

@rtimms , @jeromtom , and @tinosulzer Thanks for letting me know, I have made the changes as a part of pull request abiove. Could you please review it once? Thanks in Advance!

[arjxn-py]

@rtimms If noone is working on this issue, I'd like to give it a try.

[rtimms]

Hi @arjxn-py it looks like @jaskiratsingh2000 is no longer working on this, so feel free to pick it up. There is an open PR #2709 that may help. Thanks!

[arjxn-py]

Thanks @tinosulzer, I was really stuck at this.

[valentinsulzer]

Yeah it was getting a bit messy with all the different interpolants, switching to xarray made it much easier