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
269297904,MDU6SXNzdWUyNjkyOTc5MDQ=,1666,Could a DataArrayRolling object compute an arbitrary function on rolling windows?,8944955,closed,0,,,14,2017-10-28T08:53:16Z,2020-11-25T00:08:45Z,2020-11-25T00:08:45Z,NONE,,,,"What I'd like to do is something of this kind

#### Code Sample, a copy-pastable example if possible

```python
da = xr.DataArray(range(10))
r = da.rolling(dim_0=2)

def func(x, axis, **kwargs):
    return x/x[-1] # for example

# This is the desired functionality
generator = r.map(func)
func_on_window = generator.next() # each time this is called, the rolling object returns func(window,...)
```

#### Desired output
```python
generator.next()
# [0,1]
generator.next()
# [0.5,1]
generator.next()
# [0.6666...,1]
...
```

This would be extremely useful to pipe data directly into a neural network for instance.","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/1666/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue