title: How to read the coordinate values of a repeated first string in xarray?
body: <p>The xarray is two dimensional (storm*time) with coordinates time, lat, and lon. I am trying to get the corresponding coordinates values of the first repeated value in xarray.</p>
  <p>In other words, In the xarray there are nan values and repeated values of b'TD'. I want to get the time, lat, and lon values of the first b'TD' in each storm.</p>
  <p>Here is the output of a xarray.</p>
  <blockquote>
  <p>&lt;xarray.DataArray 'usa_status' (storm: 17, date_time: 36)&gt;
  array([[nan, nan, b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD',
  b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan],
  [nan, nan, b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, b'TD', b'TD', b'TD',
  b'TD', nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, b'TD', b'TD', nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD',
  b'TD', b'TD', b'TD', b'TD', b'TD', nan, nan, nan, nan, b'TD',
  b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD',
  b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD'],
  [b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  b'TD', b'TD', b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD', b'TD',
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan],
  [nan, nan, nan, nan, nan, nan, b'TD', b'TD', nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, b'TD', nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, b'TD', b'TD', nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, b'TD', b'TD', nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, b'TD', b'TD', b'TD', b'TD', b'TD',
  b'TD', nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan],
  [nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan,
  nan, b'TD', b'TD', b'TD', b'TD', nan, nan, nan, nan, nan, nan,
  nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan, nan]],
  dtype=object)
  Coordinates:
  time     (storm, date_time) datetime64[ns] 2017-07-05T12:00:00.000039936 ... 2019-09-26T03:00:00.000039936
  lat      (storm, date_time) float32 11.8 11.880182 12.0 ... 14.5 14.634828
  lon      (storm, date_time) float32 -35.9 -36.475014 ... -37.6 -38.230053
  Dimensions without coordinates: storm, date_time
  Attributes:
  long_name:              Storm status
  description:             DB - disturbance,  TD - tropical depression,  TS...
  coverage_content_type:  thematicClassification</p>
  </blockquote>