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
163414759,MDU6SXNzdWUxNjM0MTQ3NTk=,894,Dataset variable reference fails after renaming,17951292,closed,0,,,4,2016-07-01T15:04:15Z,2016-08-02T17:39:11Z,2016-08-02T17:39:11Z,NONE,,,,"Using xarray v0.7.2, I've encountered what looks to be a bug whereby referencing a re-named variable raises a KeyError:
# compute anomalies

climo = ds.groupby('time.dayofyear').mean('time')
anom = ds.groupby('time.dayofyear') - climo
anom.rename({'air': 't2manom'})

**# Output** 

 _<xarray.Dataset>
Dimensions:    (lat: 37, level: 1, lon: 192, time: 13514)
Coordinates:
- lat        (lat) float32 88.542 86.6531 84.7532 82.8508 80.9473 79.0435 ...
- level      (level) float32 2.0
- lon        (lon) float32 0.0 1.875 3.75 5.625 7.5 9.375 11.25 13.125 ...
  dayofyear  (time) int32 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 ...
- time       (time) datetime64[ns] 1979-01-01 1979-01-02 1979-01-03 ...
  Data variables:
  t2manom    (time, level, lat, lon) float64 -6.342 -6.476 -6.522 -6.579 ..._

anom['t2manom'].values[0:5]

**Output:**

_---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-10-05206d711de3> in <module>()
      8 #del normalized['dayofyear']
      9 #normalized
---> 10 anom['t2manom'].values[0:5]

/usr/local/lib/python2.7/dist-packages/xarray/core/dataset.pyc in **getitem**(self, key)
    527 
    528         if hashable(key):
--> 529             return self._construct_dataarray(key)
    530         else:
    531             return self._copy_listed(np.asarray(key))

/usr/local/lib/python2.7/dist-packages/xarray/core/dataset.pyc in _construct_dataarray(self, name)
    476             variable = self._variables[name]
    477         except KeyError:
--> 478             _, name, variable = _get_virtual_variable(self._variables, name)
    479 
    480         coords = OrderedDict()

/usr/local/lib/python2.7/dist-packages/xarray/core/dataset.pyc in _get_virtual_variable(variables, key)
     43     split_key = key.split('.', 1)
     44     if len(split_key) != 2:
---> 45         raise KeyError(key)
     46 
     47     ref_name, var_name = split_key

KeyError: 't2manom'_

However, referencing the OLD variable name ('air' in this case) produces the output expected when referencing the NEW variable name:

anom['air'].values[0:5]

**Output:**

array([[[[ -6.34243229,  -6.47621607,  -6.52189175, ...,  -6.3105404 ,
           -6.33972959,  -6.30999986],
         [ -9.18891871,  -9.32432412,  -9.57216195, ...,  -8.67081062,
           -8.89675656,  -9.09081061],
         [ -8.8072971 ,  -9.27054033,  -9.69972951, ...,  -7.53378362,
           -7.93783766,  -8.3737836 ],
         ..., 
         [ -4.30864855,  -3.5656756 ,  -1.10594592, ...,  -1.70405402,
           -2.53135129,  -2.92999993],
         [ -1.197027  ,  -1.34837835,  -0.5481081 , ...,   0.01810811,
            0.01540541,  -0.62756755],
         [  0.47135134,   0.22297297,  -0.50756756, ...,   0.63297296,
            0.65837836,   0.58891891]]],

[...omitted values...]

Am I doing something wrong here?
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167684282,MDU6SXNzdWUxNjc2ODQyODI=,919,ValueError: encountered unexpected variable nbnds,17951292,closed,0,,,3,2016-07-26T18:59:02Z,2016-07-27T22:37:02Z,2016-07-27T22:37:02Z,NONE,,,,"Using the recipe presented near the bottom of http://xarray.pydata.org/en/stable/io.html for reading in multiple files via opendap, I encounter the error referenced in the subject line. 

Here is the call to read_netcdfs:

base = 'http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis.dailyavgs/surface_gauss/air.2m.gauss.%4u.nc'
files = [base % d for d in range(1948,2016,1)]
ds_combined = read_netcdfs(files,dim='time',transform_func=None)

I am using option decode_cf=False in xr.open_dataset

Here is the entire content of the error message:

ValueError                                Traceback (most recent call last)
<ipython-input-5-024a3f9ac990> in <module>()
      2 base = 'http://www.esrl.noaa.gov/psd/thredds/dodsC/Datasets/ncep.reanalysis.dailyavgs/surface_gauss/air.2m.gauss.%4u.nc'
      3 files = [base % d for d in range(1948,2016,1)]
----> 4 ds_combined = read_netcdfs(files,dim='time',transform_func=None)

<ipython-input-4-36b274dcd63c> in read_netcdfs(files, dim, transform_func)
     18         paths = files
     19     datasets = [process_one_path(p) for p in paths]
---> 20     combined = xr.concat(datasets, dim)
     21     return combined

/usr/local/lib/python2.7/dist-packages/xarray/core/combine.pyc in concat(objs, dim, data_vars, coords, compat, positions, indexers, mode, concat_over)
    112         raise TypeError('can only concatenate xarray Dataset and DataArray '
    113                         'objects, got %s' % type(first_obj))
--> 114     return f(objs, dim, data_vars, coords, compat, positions)
    115 
    116 

/usr/local/lib/python2.7/dist-packages/xarray/core/combine.pyc in _dataset_concat(datasets, dim, data_vars, coords, compat, positions)
    231         for k, v in iteritems(ds.variables):
    232             if k not in result_vars and k not in concat_over:
--> 233                 raise ValueError('encountered unexpected variable %r' % k)
    234             elif (k in result_coord_names) != (k in ds.coords):
    235                 raise ValueError('%r is a coordinate in some datasets but not '

ValueError: encountered unexpected variable u'nbnds'

Any ideas as to how I can avoid triggering this error?
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162726984,MDU6SXNzdWUxNjI3MjY5ODQ=,891,BUG: Test for dask version erroneously fails when calling xr.mfdataset(),17951292,closed,0,,,2,2016-06-28T16:17:16Z,2016-07-20T04:29:34Z,2016-07-20T04:29:34Z,NONE,,,,"I have latest version of dask installed but get the following exception when using xr.mfdataset():
'ImportError: xarray requires dask version 0.6 or newer'

Problem appears to be due to the fact that the latest version is 0.10 (i.e., dask.**version** =  '0.10.0') but exception is raised since 0.1 < 0.6
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/891/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
166195300,MDU6SXNzdWUxNjYxOTUzMDA=,900,How to apply function to two (or more) variables simultaneously,17951292,closed,0,,,3,2016-07-18T21:14:57Z,2016-07-19T01:31:46Z,2016-07-19T01:31:40Z,NONE,,,,"I have two datasets: fcst and obs, each with dimensions (time, lat, lon). The first contains predicted values on a lat x lon grid for a given lead time and the second the corresponding verifying observations. I want to compute skill scores at each time but this obviously involves applying a function involving variables from both datasets. Moreover, the two fields (fcst and obs) need to be cosine weighted first (involves coordinate 'lat'). Furthermore, I wish to align the forecasts and obs in time; there may be missing values of each at different times. I tried aligning the datasets using 'xr.align' but got all kinds of errors when trying to use the resulting new dataset. I suppose I could extract the values from each dataset, taking care to use indexing to extract the common times and then using standard numpy operations and the like but before I go that route is there a methodology for using xarray to do such a computation? If I were doing a single variable computation, it would be easy to use the groupby and apply methods. TIA for any advice!
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