Allow make_xarray_grid to take horizontal coordinates as 1d arrays

[santisoler]

Now make_xarray_grid could take 1d arrays for horizontal coordinates, such as
how xr.DataArray stores the single dimension coordinates. Add a new
non-public meshgrid_to_1d function to convert 2d meshgrids (like the ones
generated by vd.grid_coordinates) to 1d arrays containing a single coordinate
of the corresponding axis. This function checks if all elements inside the 2d
array are equal along the right axis, i.e. a vaild meshgrid.

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[leouieda]

Looks really good @santisoler! Just a few minor suggestions and feel free to merge afterwards.

[santisoler]

@leouieda Since we renamed the check function to check_regular_grid I added an additional check: if the horizontal coordinates of a regular grid are evenly spaced.

[leouieda]

@santisoler i don’t think that check is necessary since we can still do the conversion to xarray if the spacing is variable. So maybe that function could really be check_meshgrid since it just needs to verify that the 2D arrays come from a meshgrid call. Sorry about that 🙂

[santisoler]

@santisoler i don’t think that check is necessary since we can still do the conversion to xarray if the spacing is variable. So maybe that function could really be check_meshgrid since it just needs to verify that the 2D arrays come from a meshgrid call. Sorry about that slightly_smiling_face

No problem! I though the same when I named the function. When you suggested to change it to check_regular_grid I though the function should also check if the coordinates are actually evenly spaced. But you're right, for the purpose of the function it's ok to just check if the 2d-arrays are returns from a meshgrid call.

Let me revert the changes and rename the function to check_meshgrid.

[leouieda]

👍🏽 this seems good to go!