html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/742#issuecomment-242235696,https://api.github.com/repos/pydata/xarray/issues/742,242235696,MDEyOklzc3VlQ29tbWVudDI0MjIzNTY5Ng==,8982598,2016-08-24T23:05:49Z,2016-08-24T23:05:49Z,CONTRIBUTOR,"@shoyer My 2 cents for how this might work after 0.8+ (auto-align during `concat`, `merge` and `auto_combine` goes a long to solving this already) is that the `compat` option of `merge` etc could have a 4th option `'nonnull_equals'` (or better named...),  with compatibility tested by e.g.

``` python
import xarray.ufuncs as xrufuncs

def nonnull_compatible(first, second):
    """""" Check whether two (aligned) datasets have any conflicting non-null values. """"""

    # mask for where both objects are not null
    both_not_null = xrufuncs.logical_not(first.isnull() | second.isnull())

    # check remaining values are equal
    return first.where(both_not_null).equals(second.where(both_not_null))
```

And then `fillna` to combine variables. Looking now I think this is very similar to what you are suggesting in #835.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,130753818
https://github.com/pydata/xarray/issues/742#issuecomment-227573330,https://api.github.com/repos/pydata/xarray/issues/742,227573330,MDEyOklzc3VlQ29tbWVudDIyNzU3MzMzMA==,8982598,2016-06-21T21:11:21Z,2016-06-21T21:11:21Z,CONTRIBUTOR,"Woops - I actually meant to put

``` python
ds['var'].loc[{...}]
```

in there as the one that works ... my understanding is that this is supported as long as the specified coordinates are 'nice' (according to `pandas`) slices/scalars. 

And yes, default values for DataArray/Dataset would definitely fill the ""create_all_missing"" need.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,130753818
https://github.com/pydata/xarray/issues/742#issuecomment-226547071,https://api.github.com/repos/pydata/xarray/issues/742,226547071,MDEyOklzc3VlQ29tbWVudDIyNjU0NzA3MQ==,8982598,2016-06-16T16:57:48Z,2016-06-16T16:57:48Z,CONTRIBUTOR,"Yes following a similar line of thought to you I recently wrote an _'all missing'_ dataset constructor (rather than _'empty'_ which I think of as no variables):

``` python
def all_missing_ds(coords, var_names, var_dims, var_types):
    """"""
    Make a dataset whose data is all missing.
    """"""
    # Empty dataset with appropirate coordinates
    ds = xr.Dataset(coords=coords)
    for v_name, v_dims, v_type in zip(var_names, var_dims, var_types):
        shape = tuple(ds[d].size for d in v_dims)
        if v_type == int or v_type == float:
            # Warn about up-casting int to float?
            nodata = np.tile(np.nan, shape)
        elif v_type == complex:
            # astype(complex) produces (nan + 0.0j)
            nodata = np.tile(np.nan + np.nan*1.0j, shape)
        else:
            nodata = np.tile(np.nan, shape).astype(object)
        ds[v_name] = (v_dims, nodata)
    return ds
```

To go with this (and this might be separate issue), a `set_value` method would be helpful --- just so that one does not have to remember which particular combination of 

``` python
ds.sel(...).var = new_values
ds.sel(...)['var'] = new_values
ds.var.sel(...) = new_values
ds['var'].sel(...) = new_values
```

guarantees assigning a new value, (currently only the last syntax I believe).
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,130753818
https://github.com/pydata/xarray/issues/742#issuecomment-226179313,https://api.github.com/repos/pydata/xarray/issues/742,226179313,MDEyOklzc3VlQ29tbWVudDIyNjE3OTMxMw==,8982598,2016-06-15T12:59:08Z,2016-06-15T12:59:08Z,CONTRIBUTOR,"Just a comment that the appearance of `object` types is likely due to the fact that numpy's `NaN`s are inherently 'floats' - so this will be an issue for any method with an intermediate `missing data' stage if non-floats are being used.

I still use use the `align` and `fillna` method since I mostly deal with floats/complex numbers, although @shoyer 's suggestion of a partial align and then `concat` could definitely be cleaner when the added coordinates are all 'new'.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,130753818