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/1914#issuecomment-366825366,https://api.github.com/repos/pydata/xarray/issues/1914,366825366,MDEyOklzc3VlQ29tbWVudDM2NjgyNTM2Ng==,6815844,2018-02-19T23:21:05Z,2018-02-19T23:34:58Z,MEMBER,"I am not sure if it is efficient to interact with a cluster, but I often use `MultiIndex` for make a cartesian product,
```python
In [1]: import xarray as xr
   ...: import numpy as np
   ...: data = xr.DataArray(np.full((3, 4), np.nan), dims=('x', 'y'), 
   ...:                     coords={'x': [0, 1, 2], 'y': ['a', 'b', 'c', 'd']})
   ...: 
   ...: data
   ...: 
Out[1]: 
<xarray.DataArray (x: 3, y: 4)>
array([[ nan,  nan,  nan,  nan],
       [ nan,  nan,  nan,  nan],
       [ nan,  nan,  nan,  nan]])
Coordinates:
  * x        (x) int64 0 1 2
  * y        (y) <U1 'a' 'b' 'c' 'd'

In [2]: data1 = data.stack(xy=['x', 'y'])
   ...: data1
   ...: 
Out[2]: 
<xarray.DataArray (xy: 12)>
array([ nan,  nan,  nan,  nan,  nan,  nan,  nan,  nan,  nan,  nan,  nan,  nan])
Coordinates:
  * xy       (xy) MultiIndex
  - x        (xy) int64 0 0 0 0 1 1 1 1 2 2 2 2
  - y        (xy) object 'a' 'b' 'c' 'd' 'a' 'b' 'c' 'd' 'a' 'b' 'c' 'd'
```
For the above example, `data` becomes 1-dimensional with coordinate `xy`, where `xy` is a product of `x` and `y`.
Each entry of `xy` is  tuple of 'x' and 'y' value,
```python
In [3]: data1[0]
Out[3]: 
<xarray.DataArray ()>
array(np.nan)
Coordinates:
    xy       object (0, 'a')
```
and we can assign a value for given coordinate values by `loc` method,
```python
In [5]: # Assuming we found the result with (1, 'a') is 2.0
   ...: data1.loc[(1, 'a'), ] = 2.0

In [6]: data1
Out[6]: 
<xarray.DataArray (xy: 12)>
array([ nan,  nan,  nan,  nan,   2.,  nan,  nan,  nan,  nan,  nan,  nan,  nan])
Coordinates:
  * xy       (xy) MultiIndex
  - x        (xy) int64 0 0 0 0 1 1 1 1 2 2 2 2
  - y        (xy) object 'a' 'b' 'c' 'd' 'a' 'b' 'c' 'd' 'a' 'b' 'c' 'd'
```

Note that we need to access via `data1.loc[(1, 'a'), ]`, rather than `data1.loc[(1, 'a')]` (last comma in the bracket is needed.)

EDIT: I modified my previous comment to take the partial assignment into accout.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,297560256