issue_comments

I guess ds = ds.drop([c for c in ds.coords if c not in ds.dims]) works. Might be nice to have a convenience function for that though.

Is there currently a way to drop unused coordinates, like this?

No worries--thanks for merging!

thanks @kmsquire, especially for your patience here!

Rebased to fix the NEWS conflict.

Hello @kmsquire! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers:

Comment last updated at 2019-03-03 02:27:43 UTC

@shoyer I force pushed the requested changes. Please let me know if there is anything else. Thanks!

I agree that it makes sense to recompute dimensions from variables.

Okay, that's what this PR already did (via the call to _replace_with_new_dims).

Rebased on master. From my perspective, this should be good to go.

It's OK to use _replace_with_new_dims still. I think we'll eventually replace it in favor of _replace_with_new_dims but we aren't there yet.

I agree that it makes sense to recompute dimensions from variables. There's not much point in keeping around extra dimensions that don't have corresponding variables, and I'm pretty sure that this is consistent with how Dataset.drop() works.

@shoyer I'm sure you're busy... wondering if you might have time to review this (or direct it to someone else to review)? Other than my question above, it should be pretty straightforward.

I was looking for this functionality and ran across #1949.

There was one bit of behavior that was unclear to me. Say I have

```python In [6]: data = xr.Dataset({'A': (['x', 'y'], np.random.randn(2, 3)), ...: 'B': ('x', np.random.randn(2)), ...: 'x': ['a', 'b'], 'z': np.pi})

In [7]: data Out[7]: <xarray.Dataset> Dimensions: (x: 2, y: 3) Coordinates: * x (x) <U1 'a' 'b' Dimensions without coordinates: y Data variables: A (x, y) float64 -0.662 -0.705 -0.1866 -0.8655 0.5816 -0.2308 B (x) float64 -0.1002 2.402 z float64 3.142

In [8]: data.drop_dims('x') Out[8]: <xarray.Dataset> Dimensions: () Data variables: z float64 3.142 ```

In this case, I dropped x, but because that eliminated variable A, I also dropped my y dimension, since A was the only variable using y.

At one point, I implemented this slightly differently, which instead gave

python In [8]: data.drop_dims('x') Out[8]: <xarray.Dataset> Dimensions: (y: 3) Dimensions without coordinates: y Data variables: z float64 3.142

In some ways, this seems preferable, especially if y has coordinates. The only downside I can see is that this version called Dataset._replace_vars_and_dims(), the docstring for which says it's deprecated (although it's still widely used).