[SOLVED] Replace xarray coordinates with another coordinate

Replace xarray coordinates with another coordinate

I try to replace two coordinates with the same length in a xarray.Dataset by using one coordinate for both of them. I do not care about the old coordinates or its values; I simply want to replace them. Is there any convenient method for this?

import xarray as xr
ds = xr.Dataset({
    "a": ("a_coord", [0, 1, 2]),
    "b": ("b_coord", [50, 10, 20]),
    "a_coord": [4, 8, 9],
    "b_coord": [3, 1, 4],
    "new_coord": [0, 1, 2],
})
# Get rid of a_coord and b_coord and replace both with new_coord, so a and b
# have new_coord as coordinate.
# But how?

I tried rename, but it returns a conflict error (since new_coord already exists).

ds.rename({
    "a_coord": "new_coord",
    "b_coord": "new_coord",
})

Do I have to assign the new coordinate explicitly to each data variable that was depended on one of the old coordinates? Since I have many data variables (not just a and b) and other coordinates, this could become messy.

Solution

You need to reset index first:

ds.reset_index(['a_coord', 'b_coord'], drop = True, inplace = True)
ds['a']= ds.a.rename({'a_coord': 'new_coord'})
ds['b']= ds.b.rename({'b_coord': 'new_coord'})