DataArray resample does not work if the time coordinate name is different from the corresponding dimension name.

Please see the example below and the output it produces. And the exception is not really helpful…

from xarray import DataArray
from datetime import datetime, timedelta


def main():
    N = 48
    data = range(N)

    dates = [datetime(2001, 1, 1) + timedelta(hours=i) for i in range(N)]

    # time variable is called the same as time dimension: works
    scheme1 = {
        "dims": "t",
        "coords": {"t": {"dims": "t", "data": dates}},
        "data": data
    }

    # time variable is called differently from the time dimension: does not work
    scheme2 = {
        "dims": "t",
        "coords": {"time": {"dims": "t", "data": dates}},
        "data": data
    }

   # Create DataArray objects using the above defined schemes
    a1 = DataArray.from_dict(scheme1)
    print(a1)
    print(a1.resample("D", "t"))
    print("=======================")

    a2 = DataArray.from_dict(scheme2)
    print(a2)
    print(a2.resample("D", "t"))


if __name__ == '__main__':
    main()

Below is the output I get from running the script:

<xarray.DataArray (t: 48)>
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
       17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
       34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47])
Coordinates:
  * t        (t) datetime64[ns] 2001-01-01 2001-01-01T01:00:00 ...
<xarray.DataArray (t: 2)>
array([ 11.5,  35.5])
Coordinates:
  * t        (t) datetime64[ns] 2001-01-01 2001-01-02
=======================
<xarray.DataArray (t: 48)>
array([ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
       17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33,
       34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47])
Coordinates:
    time     (t) datetime64[ns] 2001-01-01 2001-01-01T01:00:00 ...
  * t        (t) int64 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 ...
Traceback (most recent call last):
  File "/Users/huziy/skynet2/RESCUE/skynet3_rech1/huziy/Netbeans Projects/Python/RPN/src/demo/xarray/time_dim_and_ops.py", line 46, in <module>
    main()
  File "/Users/huziy/skynet2/RESCUE/skynet3_rech1/huziy/Netbeans Projects/Python/RPN/src/demo/xarray/time_dim_and_ops.py", line 38, in main
    print(a2.resample("D", "t"))
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/xarray/core/common.py", line 499, in resample
    gb = self.groupby_cls(self, group, grouper=time_grouper)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/xarray/core/groupby.py", line 202, in __init__
    first_items = s.groupby(grouper).first()
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/core/generic.py", line 3974, in groupby
    **kwargs)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/core/groupby.py", line 1501, in groupby
    return klass(obj, by, **kwds)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/core/groupby.py", line 370, in __init__
    mutated=self.mutated)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/core/groupby.py", line 2403, in _get_grouper
    binner, grouper, obj = key._get_grouper(obj)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/tseries/resample.py", line 1061, in _get_grouper
    r = self._get_resampler(obj)
  File "/Users/huziy/virtualenvs/py3.4/lib/python3.4/site-packages/pandas/tseries/resample.py", line 1057, in _get_resampler
    "but got an instance of %r" % type(ax).__name__)
TypeError: Only valid with DatetimeIndex, TimedeltaIndex or PeriodIndex, but got an instance of 'Int64Index'

[shoyer]

@chrwerner Yes, exactly.

[stale[bot]]

In order to maintain a list of currently relevant issues, we mark issues as stale after a period of inactivity

If this issue remains relevant, please comment here or remove the stale label; otherwise it will be marked as closed automatically