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/7076#issuecomment-1431400086,https://api.github.com/repos/pydata/xarray/issues/7076,1431400086,IC_kwDOAMm_X85VUW6W,18679148,2023-02-15T13:49:45Z,2023-02-16T13:43:29Z,NONE,"Hi @DWesl, @benbovy 

I got a bug very similar to what was initially report with the following minimal example (xarray version 2022.11.0) with the error:
> ValueError: cannot unstack dimensions that do not have exactly one multi-index: ('z',)

It is working fine with my previous version (xarray 0.16.0)
```python
import xarray as xr
ds = xr.Dataset(
    data_vars=dict(
        mydata = ( ['across', 'along'], [[0,1],[2,3]])
    )
)
stacked = ds.stack(z=(""across"", ""along""))
newlist = [None] * stacked.z.size
for ii, zindex in enumerate(stacked.z.data):
    newlist[ii] = stacked.mydata.sel(z=zindex)
newds = xr.concat(newlist, dim='z')
newds['z'] = stacked.z
print('xarray version:' + xr.__version__)
newds.unstack(dim='z')
```

If I do `newds = newds.reset_index('z')` just before the last line, it is solved for my minimal example. But it still doesn't work for my real problem and I don't think it is the best way to proceed.

Many thanks for your help,
Adrien




","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1384465119
https://github.com/pydata/xarray/issues/7076#issuecomment-1433104955,https://api.github.com/repos/pydata/xarray/issues/7076,1433104955,IC_kwDOAMm_X85Va3I7,18679148,2023-02-16T13:41:12Z,2023-02-16T13:41:12Z,NONE,"> 

Hi @benbovy, my code works for 2 dimensions, but it doesn't with 1D. I think the error comes from `.set_index(z=['across'])` which delivers a ""PandasIndex(Int64Index("" and not the expected ""PandasIndex(MultiIndex("" for `unstack`.

I created a Pandas-MultiIndex ""MultiIndex([((0,), (1,))], names=['z', 'across'])"" (see code just below), but it is not exactly the same one as the one created by `.stack()` ""PandasIndex(MultiIndex([(0,),(1,)], name='z'))"" and I didn't find out how to pass the 'index' to xarray.
```python
import pandas as pd
tuples = [(0,),(1,)],
index = pd.MultiIndex.from_tuples(tuples, names=[""z"",""across""])
index
```

My modified minimal example is as below:
```python
import xarray as xr
ds = xr.Dataset(
    data_vars=dict(
        mydata = ( ['across', 'along'], [[0,1],[2,3]])
    ),
    coords=dict( # <- changed 
        across=[0,1], # <- changed 
        along=[0,1], # <- changed 
    ),    # <- changed
)
stacked = ds.isel(along=0).stack(z=[""across""]) # <- changed
newlist = [None] * stacked.z.size
for ii, zindex in enumerate(stacked.z.data):
    newlist[ii] = stacked.mydata.sel(z=zindex)
newds = xr.concat(newlist, dim='z')
newds = newds.set_index(z=['across']) # <- changed
newds.unstack(dim='z') # Fail with ValueError: cannot unstack dimensions that do not have exactly one multi-index: ('z',)
```



","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1384465119
https://github.com/pydata/xarray/issues/7076#issuecomment-1431736710,https://api.github.com/repos/pydata/xarray/issues/7076,1431736710,IC_kwDOAMm_X85VVpGG,18679148,2023-02-15T17:24:27Z,2023-02-15T17:24:27Z,NONE,"> Many thanks for the explanation and the rapid answer. I am not very familiar with multi-index.
> 
> My real problem works with a DataSet with different sort of variables:
> 
> ```
> ipdb> lmmap
> <xarray.Dataset>
> Dimensions:        (x_variables: 4, Observables: 2, Antenna: 4, z: 4,
>                     Ambiguities: 4, fun_variables: 8, extrema: 2)
> Coordinates:
>   * x_variables    (x_variables) <U3 'u' 'v' 'c_u' 'c_v'
>   * Observables    (Observables) <U6 'sigma0' 'RVL'
>   * Antenna        (Antenna) <U4 'Fore' 'MidV' 'MidH' 'Aft'
>     fun_variables  (Observables, Antenna) int64 0 1 2 3 4 5 6 7
> Dimensions without coordinates: z, Ambiguities, extrema
> Data variables: (12/17)
>     x              (z, Ambiguities, x_variables) float64 -4.503 7.8 ... -0.4265
>     active_mask    (z, Ambiguities, x_variables) int64 0 0 0 0 0 0 ... 0 0 0 0 0
>     grad           (z, Ambiguities, x_variables) float64 7.816e-11 ... -1.873...
>     fun            (z, Ambiguities, Observables, Antenna) float64 0.001137 .....
>     jac            (z, Ambiguities, fun_variables, x_variables) float64 0.359...
>     x0             (z, Ambiguities, x_variables) float64 -7.002 10.03 ... 1.219
>     ...             ...
>     message        (z, Ambiguities) <U42 '`xtol` termination condition is sat...
>     success        (z, Ambiguities) bool True True True True ... True True True
>     method         (z) <U3 'trf' 'trf' 'trf' 'trf'
>     xtol           (z) float64 0.001 0.001 0.001 0.001
>     x_scale        (z, x_variables) float64 7.0 7.0 0.5 0.5 ... 7.0 7.0 0.5 0.5
>     bounds         (z, extrema, x_variables) int64 -30 -30 -5 -5 ... 30 30 5 5
> ```
> 
> I don't know where I should apply `set_index(z=[""across"", ""along""])` I tried on the full DataSet or a single DataArray but without success. I get the following error:
> 
> > ValueError: across, along variable(s) do not exist
> 
> Which is obvious as across and along variables disappeared. Thank you, I will dig in this direction why it happens.
> 
> However, it works perfectly with the minimal example. Many thanks

Thanks @benbovy, my issue is now resolved, once I have enabled the coords to follow.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1384465119
https://github.com/pydata/xarray/issues/7076#issuecomment-1431676036,https://api.github.com/repos/pydata/xarray/issues/7076,1431676036,IC_kwDOAMm_X85VVaSE,18679148,2023-02-15T16:51:49Z,2023-02-15T16:51:49Z,NONE,I didn't see any warning for this,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1384465119
https://github.com/pydata/xarray/issues/7076#issuecomment-1431529928,https://api.github.com/repos/pydata/xarray/issues/7076,1431529928,IC_kwDOAMm_X85VU2nI,18679148,2023-02-15T15:15:23Z,2023-02-15T15:20:58Z,NONE,"Many thanks for the explanation and the rapid answer. I am not very familiar with multi-index.

My real problem works with a DataSet with different sort of variables:

```
ipdb> lmmap
<xarray.Dataset>
Dimensions:        (x_variables: 4, Observables: 2, Antenna: 4, z: 4,
                    Ambiguities: 4, fun_variables: 8, extrema: 2)
Coordinates:
  * x_variables    (x_variables) <U3 'u' 'v' 'c_u' 'c_v'
  * Observables    (Observables) <U6 'sigma0' 'RVL'
  * Antenna        (Antenna) <U4 'Fore' 'MidV' 'MidH' 'Aft'
    fun_variables  (Observables, Antenna) int64 0 1 2 3 4 5 6 7
Dimensions without coordinates: z, Ambiguities, extrema
Data variables: (12/17)
    x              (z, Ambiguities, x_variables) float64 -4.503 7.8 ... -0.4265
    active_mask    (z, Ambiguities, x_variables) int64 0 0 0 0 0 0 ... 0 0 0 0 0
    grad           (z, Ambiguities, x_variables) float64 7.816e-11 ... -1.873...
    fun            (z, Ambiguities, Observables, Antenna) float64 0.001137 .....
    jac            (z, Ambiguities, fun_variables, x_variables) float64 0.359...
    x0             (z, Ambiguities, x_variables) float64 -7.002 10.03 ... 1.219
    ...             ...
    message        (z, Ambiguities) <U42 '`xtol` termination condition is sat...
    success        (z, Ambiguities) bool True True True True ... True True True
    method         (z) <U3 'trf' 'trf' 'trf' 'trf'
    xtol           (z) float64 0.001 0.001 0.001 0.001
    x_scale        (z, x_variables) float64 7.0 7.0 0.5 0.5 ... 7.0 7.0 0.5 0.5
    bounds         (z, extrema, x_variables) int64 -30 -30 -5 -5 ... 30 30 5 5
```

I don't know where I should apply `set_index(z=[""across"", ""along""])` I tried on the full DataSet or a single DataArray but without success. I get the following error:

> ValueError: across, along variable(s) do not exist

Which is obvious as across and along variables disappeared. Thank you, I will dig in this direction why it happens.

However, it works perfectly with the minimal example.
Many thanks

","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,1384465119
https://github.com/pydata/xarray/issues/2304#issuecomment-852069023,https://api.github.com/repos/pydata/xarray/issues/2304,852069023,MDEyOklzc3VlQ29tbWVudDg1MjA2OTAyMw==,18679148,2021-06-01T12:03:55Z,2021-06-07T20:48:00Z,NONE,"Dear all and thank you for your work on Xarray,

Link to @magau comment, I have a netcdf with multiple variables in different format (float, short, byte).
Using open_mfdataset 'short' and 'byte' are converted in 'float64' (no scaling, but some masking for the float data).
It doesn't raise major issue for me, but it is taking plenty of memory space for nothing.

Below an example of the 3 format from (ncdump -h):
```
	short total_nobs(time, lat, lon) ;
		total_nobs:long_name = ""Number of SSS in the time interval"" ;
		total_nobs:valid_min = 0s ;
		total_nobs:valid_max = 10000s ;
	float pct_var(time, lat, lon) ;
		pct_var:_FillValue = NaNf ;
		pct_var:long_name = ""Percentage of SSS_variability that is expected to be not explained by the products"" ;
		pct_var:units = ""%"" ;
		pct_var:valid_min = 0. ;
		pct_var:valid_max = 100. ;
	byte sss_qc(time, lat, lon) ;
		sss_qc:long_name = ""Sea Surface Salinity Quality, 0=Good; 1=Bad"" ;
		sss_qc:valid_min = 0b ;
		sss_qc:valid_max = 1b ;
```

And how they appear after opening in as xarray using open_mfdataset:
```
total_nobs (time, lat, lon) float64 dask.array<chunksize=(48, 584, 1388), meta=np.ndarray>
pct_var (time, lat, lon) float32 dask.array<chunksize=(48, 584, 1388), meta=np.ndarray>
sss_qc (time, lat, lon) float64 dask.array<chunksize=(48, 584, 1388), met
```

Is there any recommandation?
Regards","{""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,343659822
https://github.com/pydata/xarray/issues/4246#issuecomment-663171676,https://api.github.com/repos/pydata/xarray/issues/4246,663171676,MDEyOklzc3VlQ29tbWVudDY2MzE3MTY3Ng==,18679148,2020-07-23T18:46:51Z,2020-07-23T18:46:51Z,NONE,thank you for the suggestion,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,663649344
https://github.com/pydata/xarray/issues/4247#issuecomment-662503816,https://api.github.com/repos/pydata/xarray/issues/4247,662503816,MDEyOklzc3VlQ29tbWVudDY2MjUwMzgxNg==,18679148,2020-07-22T14:59:16Z,2020-07-22T14:59:16Z,NONE,"With your explanation, it is now clearer and it works fine. 
If it is possible to add your sentence explanation to the `ValueError` it could be good.
Many thanks for your help.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,663769801