issue_comments: 793204639

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https://github.com/pydata/xarray/issues/5012#issuecomment-793204639 https://api.github.com/repos/pydata/xarray/issues/5012 793204639 MDEyOklzc3VlQ29tbWVudDc5MzIwNDYzOQ== 3460034 2021-03-09T00:38:37Z 2021-03-09T00:39:02Z CONTRIBUTOR

I'll leave the exact issue up to someone more acquainted with string and slice handling on TimedeltaIndex, but in case it is useful, here are two things I noticed (to hopefully speed along the troubleshooting):

1) Using pandas Timedeltas instead of strings (i.e., ds.sel(time=slice(pd.Timedelta("01:00:00"), pd.Timedelta("01:15:00")))) works, giving

<xarray.Dataset> Dimensions: (time: 39, yh: 1, zh: 1) Coordinates: xh float32 ... * yh (yh) float32 0.0 * zh (zh) float32 0.0 * time (time) timedelta64[ns] 01:00:00 01:07:30 ... 01:14:30 01:15:00 Data variables: (12/26) x (time) float32 ... y (time) float32 ... z (time) float32 ... u (time) float32 ... v (time) float32 ... w (time) float32 ... ... ... b (time) float32 ... vpg (time) float32 ... zvort (time) float32 ... rho (time) float32 ... qsl (time) float32 ... qsi (time) float32 ... Attributes: CM1 version: cm1r20.1 Conventions: CF-1.7 missing_value: -999999.9

However, notice that jump in the time coordinate...which leads to

2) In the failing example, the time coordinate is non-monotonic. If we .sortby('time'), then ds.sel(time=slice("01:00:00","01:15:00")) works as expected:

<xarray.Dataset> Dimensions: (time: 47, yh: 1, zh: 1) Coordinates: xh float32 1.0 * yh (yh) float32 0.0 * zh (zh) float32 0.0 * time (time) timedelta64[ns] 01:00:00 01:00:30 ... 01:15:00 01:15:30 Data variables: (12/26) x (time) float32 ... y (time) float32 ... z (time) float32 ... u (time) float32 ... v (time) float32 ... w (time) float32 ... ... ... b (time) float32 ... vpg (time) float32 ... zvort (time) float32 ... rho (time) float32 ... qsl (time) float32 ... qsi (time) float32 ... Attributes: CM1 version: cm1r20.1 Conventions: CF-1.7 missing_value: -999999.9

(the working example also has a monotonic time coordinate)

And so, I would guess this is an example of string-based timedelta selection failing on non-monotonic coordinates.

 
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