id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
178200674,MDU6SXNzdWUxNzgyMDA2NzQ=,1013,Groupby exclude dimension,4295853,open,0,,,8,2016-09-20T22:48:46Z,2020-10-04T16:05:06Z,,CONTRIBUTOR,,,,"Is there some way to do a groupby operation where some dimension is excluded from the operation, e.g., a vectorized version of something like this:

``` python
vertlevels = [ds.vel.sel(nVertLevels=i).groupby('y').mean() for i in ds.nVertLevels]
xavgvel = xr.concat(vertlevels, 'nVertLevels')
```

The application here is to average 3D data in the x coordinate to the unique y coordinates, but not the vertical coordinate.  

Thus, we are basically looking for something that allows a coordinate to be excluded from the groupby operation, e.g., in this case the vertical coordinate.  Ideally this would also be possible within the context of the `groupby_bins` operation.

Any ideas on how this should work or a pointer on how to implement this type of operation more cleanly with existing infrastructure is greatly appreciated.  This appears to be related to  #324 and especially (perhaps identically) #924.

cc @vanroekel, @shoyer, @jhamman, @rabernat, @MaximilianR 
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/1013/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue
217584777,MDU6SXNzdWUyMTc1ODQ3Nzc=,1335,`cumsum` providing correct behavior for non-coordinate DataArrays?,4295853,open,0,,,5,2017-03-28T14:45:12Z,2019-03-31T05:41:09Z,,CONTRIBUTOR,,,,"In the case of a DataArray without coordinates, should cumsum work without specifying an axis, e.g., `da.cumsum()` is valid?  This is not currently the obtained behavior.

```python
In [1]: import xarray as xr
imp
In [2]: import numpy as np

In [3]: da = xr.DataArray(np.arange(10))

In [4]: da
Out[4]: 
<xarray.DataArray (dim_0: 10)>
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
Dimensions without coordinates: dim_0

In [5]: da.cumsum(axis=0)
Out[5]: 
<xarray.DataArray (dim_0: 10)>
array([ 0,  1,  3,  6, 10, 15, 21, 28, 36, 45])
Dimensions without coordinates: dim_0

In [6]: da.cumsum()
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-5-4ff0efc782ee> in <module>()
----> 1 da.cumsum()

/Users/pwolfram/src/xarray/xarray/core/common.pyc in wrapped_func(self, dim, axis, skipna, keep_attrs, **kwargs)
     17                              keep_attrs=False, **kwargs):
     18                 return self.reduce(func, dim, axis, keep_attrs=keep_attrs,
---> 19                                    skipna=skipna, allow_lazy=True, **kwargs)
     20         else:
     21             def wrapped_func(self, dim=None, axis=None, keep_attrs=False,

/Users/pwolfram/src/xarray/xarray/core/dataarray.pyc in reduce(self, func, dim, axis, keep_attrs, **kwargs)
   1146             summarized data and the indicated dimension(s) removed.
   1147         """"""
-> 1148         var = self.variable.reduce(func, dim, axis, keep_attrs, **kwargs)
   1149         return self._replace_maybe_drop_dims(var)
   1150 

/Users/pwolfram/src/xarray/xarray/core/variable.pyc in reduce(self, func, dim, axis, keep_attrs, allow_lazy, **kwargs)
    898             if dim is None and axis is None:
    899                 raise ValueError(""must supply either single 'dim' or 'axis' ""
--> 900                                  ""argument to %s"" % (func.__name__))
    901 
    902         if dim is not None:

ValueError: must supply either single 'dim' or 'axis' argument to cumsum

```","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/1335/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,issue