Preserve Coordinates when Indexing UxDataArray

[philipc2]

Closes #945

Overview

• Preserves coordinates when indexing a UxDataArray

[ahijevyc]

Looks good. I tested the change and tried to replicate the issue I had #818 with the uxarray.UxDataArray.Indexes disappearing but had no problems.

However, given this fix, I can think of two other places a similar change might be needed:

uxarray/uxarray/remap/nearest_neighbor.py

Line 110 in ec5cc8f

coords=source_uxda.coords,

and

uxarray/uxarray/remap/inverse_distance_weighted.py

Line 151 in ec5cc8f

coords=source_uxda.coords,

[philipc2]

Looks good. I tested the change and tried to replicate the issue #818 with the uxarray.UxDataArray.Indexes disappearing but had no problems.

However, given this fix, I can think of two other places a similar change might be needed:

uxarray/uxarray/remap/nearest_neighbor.py

Line 110 in ec5cc8f

coords=source_uxda.coords,

and

uxarray/uxarray/remap/inverse_distance_weighted.py

Line 151 in ec5cc8f

coords=source_uxda.coords,

Good catches, I'll update these also.

[philipc2]

@ahijevyc

When remapping, should the coordinates from the original data array be dropped? It wouldn't make much sense to preserve them (unless I'm understanding it wrong), since the coordinates from the original array are no longer representative of the new remapped grid.

[ahijevyc]

The spatial coordinates should not be transferred, but if there are non-spatial coordinates like time, ensemble_member, or forecast_hour, then those should be transferred to the destination. I think that's why I originally thought the coords argument was necessary.

[philipc2]

The spatial coordinates should not be transferred, but if there are non-spatial coordinates like time, ensemble_member, or forecast_hour, then those should be transferred to the destination. I think that's why I originally thought the coords argument was necessary.

That makes sense! I wasn't considering the non-spatial cases.

[ahijevyc]

I provided a way to drop the remapped coordinate (which I agree, should not get transferred from the source) and still preserve any non-spatial coordinates.

[ahijevyc]

@philipc2 Here's my solution to preserve any non-spatial coordinates (like time or ensemble_member) while dropping the spatial one:

Copy source_uxda.coords to a new xarray.Coordinates object. Then delete the key associated with the spatial dimension. Then use that new object as the coords argument to uxarray.core.dataarray.UxDataArray.

    destination_coords = source_uxda.coords
    del(destination_coords[destination_dim])

    # construct data array for remapping variable
    uxda_remap = uxarray.core.dataarray.UxDataArray(
        data=destination_data,
        name=source_uxda.name,
        coords=destination_coords,

Does this make sense?