issue_comments: 367380855

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https://github.com/pydata/xarray/issues/1931#issuecomment-367380855 https://api.github.com/repos/pydata/xarray/issues/1931 367380855 MDEyOklzc3VlQ29tbWVudDM2NzM4MDg1NQ== 25473287 2018-02-21T16:17:44Z 2018-02-21T16:17:44Z NONE

@jhamman @rabernat Thanks for the help!

Raising an error when encountering this issue and adding keep_core_coords=False to optionally drop the coordinate would be a good solution for me.

But is there any case that we do want to keep the core coordinate? Since input_core_dims means "dimensions that should not be broadcast", I suppose that the output DataArray has no way to inherit these non-broadcasting dimensions? Should the core coordinate just be dropped by default?

Another more basic issue: Users are allowed the mess-up the coordinate dimension of an existing DataArray. Is this an expected behavior?

``` In [1]: import xarray as xr

In [2]: xr.DataArray([0, 1, 2, 3], dims='x', coords={'x':[0, 1]}) # this is not allowed (...) ValueError: conflicting sizes for dimension 'x': length 4 on the data but length 2 on coordinate 'x'

In [3]: dr = xr.DataArray([0, 1, 2, 3], dims='x', coords={'x':[0, 1, 2, 3]})

In [4]: dr['x'] = [0, 1] # but you can mess-up the coordinate dimension afterwards

In [5]: dr Out[5]: <xarray.DataArray (x: 4)> array([0, 1, 2, 3]) Coordinates: * x (x) int64 0 1

In [6]: dr.to_netcdf('wrong_coordinate.nc') (...) ValueError: conflicting sizes for dimension 'x': length 4 on 'xarray_dataarray_variable' and length 2 on 'x' ```

 
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