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  • xarray.Dataset.sel(time='2007-04-12') returns unexpected time dimension · 3 ✖

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  • NONE · 3 ✖
id html_url issue_url node_id user created_at updated_at ▲ author_association body reactions performed_via_github_app issue
544864012 https://github.com/pydata/xarray/issues/2213#issuecomment-544864012 https://api.github.com/repos/pydata/xarray/issues/2213 MDEyOklzc3VlQ29tbWVudDU0NDg2NDAxMg== forman 206773 2019-10-22T08:46:46Z 2019-10-22T12:09:10Z NONE

@hans-permana your example shows a different issue: indexing with a date string yields a time dimension of length 1, rather than squeezing it out

Nope, look at the screenshot again, the dimension is zero. The very similar issue (if not same) remains and should be considered a bug:

If I now use sel() with a date string without time component, I get a 3D array with zero time dimension:

However, if I use sel() with a date string with time component, I get the expected 2D array:

EDIT

It seems that if I create the cube dataset from above with a time coordinate variable whose values don't have a time component (e.g. 2018-06-26 00:00:00.000000), then both sel(time='2018-06-26') and sel(time='2018-06-26 10:23:05') work as expected and only yield 2D results.

EDIT 2

Root cause may be related to Pandas indexing using strings that encode different accuracy / resolution: http://pandas-docs.github.io/pandas-docs-travis/user_guide/timeseries.html#slice-vs-exact-match. Very contra-intuitive.

Output of xr.show_versions()

python: 3.7.3 | packaged by conda-forge | (default, Jul 1 2019, 22:01:29) [MSC v.1900 64 bit (AMD64)] python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 26 Stepping 5, GenuineIntel byteorder: little LC_ALL: None LANG: None LOCALE: None.None libhdf5: 1.10.4 libnetcdf: 4.6.2 xarray: 0.14.0 pandas: 0.25.2 numpy: 1.16.4 scipy: 1.2.1 netCDF4: 1.5.0.1 pydap: None h5netcdf: None h5py: None Nio: None zarr: 2.3.2 cftime: 1.0.3.4 nc_time_axis: None PseudoNetCDF: None rasterio: 1.0.22 cfgrib: None iris: None bottleneck: None dask: 2.6.0 distributed: 2.6.0 matplotlib: 3.0.3 cartopy: None seaborn: None numbagg: None setuptools: 41.0.1 pip: 19.0.3 conda: None pytest: 4.4.2 IPython: 7.4.0 sphinx: 2.0.1 
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   xarray.Dataset.sel(time='2007-04-12') returns unexpected time dimension 329066551
394718239 https://github.com/pydata/xarray/issues/2213#issuecomment-394718239 https://api.github.com/repos/pydata/xarray/issues/2213 MDEyOklzc3VlQ29tbWVudDM5NDcxODIzOQ== hans-permana 7643370 2018-06-05T13:55:30Z 2018-06-05T13:55:30Z NONE

@shoyer I created a notebook to reproduce this issue with self-contained dummy data and I think I know when this issue occurs.

In both cases (my original application and in the notebook example), the time dimension of the DataArray comes with time. When selecting it using .sel, when time is specified with date and time, the returned DataArray is rightly 2D. However, when the time selection includes only the date (when calling xarray.Dataset.sel), the return includes an unexpected time dimension. In the notebook example, the time dimension is 1 because it could find the right date whereas in my application, time dimension is 0 because it could not find the queried date. I am not sure what is the expected behaviour here.

 
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   xarray.Dataset.sel(time='2007-04-12') returns unexpected time dimension 329066551
394371429 https://github.com/pydata/xarray/issues/2213#issuecomment-394371429 https://api.github.com/repos/pydata/xarray/issues/2213 MDEyOklzc3VlQ29tbWVudDM5NDM3MTQyOQ== hans-permana 7643370 2018-06-04T14:19:29Z 2018-06-04T14:19:29Z NONE

@jhamman - yes I can reproduce this also in 0.10.6.

INSTALLED VERSIONS ------------------ commit: None python: 3.5.2.final.0 python-bits: 64 OS: Windows OS-release: 10 machine: AMD64 processor: Intel64 Family 6 Model 63 Stepping 2, GenuineIntel byteorder: little LC_ALL: None LANG: None LOCALE: None.None xarray: 0.10.6 pandas: 0.19.0 numpy: 1.11.3 scipy: 1.1.0 netCDF4: 1.2.2 h5netcdf: 0.2.2 h5py: 2.6.0 Nio: None zarr: None bottleneck: 1.2.1 cyordereddict: 1.0.0 dask: 0.14.1 distributed: 1.21.8 matplotlib: 2.2.2 cartopy: None seaborn: 0.8.1 setuptools: 27.2.0.post20161106 pip: 9.0.1 conda: None pytest: 3.6.0 IPython: 6.4.0 sphinx: None 
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   xarray.Dataset.sel(time='2007-04-12') returns unexpected time dimension 329066551

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