title: Numpy output using OR conditionals differ from output using np.isin
body: <p>I have an xarray.Dataset such as</p>
  
  <pre><code>&lt;xarray.Dataset&gt;
  Dimensions:    (latitude: 3259, longitude: 3699, time: 60)
  Coordinates:
    * time       (time) datetime64[ns] 2017-04-03T10:47:53.500000 ...
    * latitude   (latitude) float64 46.62 46.62 46.62 46.62 46.62 46.62 46.62 ...
    * longitude  (longitude) float64 7.82 7.82 7.82 7.82 7.82 7.821 7.821 ...
  Data variables:
      slc        (time, latitude, longitude) uint8 0 0 0 0 0 0 0 0 0 0 0 0 0 0 ...
  Attributes:
      crs:      EPSG:4326
  </code></pre>
  
  <p>I can filter it with <code>mcat = (dataset_in.slc == 9) | (dataset_in.slc == 11)</code> to get an xarray.DataArray as follows</p>
  
  <pre><code>&lt;xarray.DataArray 'slc' (time: 60, latitude: 3259, longitude: 3699)&gt;
  array([[[False, False, ..., False, False],
          [False, False, ..., False, False],
          ...,     
         ...
         [[False, False, ..., False, False],
          [False, False, ..., False, False],
          ..., 
          [False, False, ..., False, False],
          [False, False, ..., False, False]]], dtype=bool)
  Coordinates:
    * time       (time) datetime64[ns] 2017-04-03T10:47:53.500000 ...
    * latitude   (latitude) float64 46.62 46.62 46.62 46.62 46.62 46.62 46.62 ...
    * longitude  (longitude) float64 7.82 7.82 7.82 7.82 7.82 7.821 7.821 ...
  </code></pre>
  
  <p>But I would need more flexibility and use instead of the OR conditionals the following code</p>
  
  <pre><code>monit_cats = [9,11]
  mcat = np.isin(dataset_in.slc, monit_cats)
  </code></pre>
  
  <p>Unfortunately I get a "simple" numpy.ndarray</p>
  
  <pre><code>[[[False False False ..., False False False]
    [False False False ..., False False False]
    [False False False ..., False False False]
    ..., 
    ...
    ..., 
    [False False False ..., False False False]
    [False False False ..., False False False]
    [False False False ..., False False False]]]
  </code></pre>
  
  <p>How could I get the exact same first output (in xarray.DataArray format)?</p>
  
  <p>Thanks for any info.</p>