html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/3290#issuecomment-529164506,https://api.github.com/repos/pydata/xarray/issues/3290,529164506,MDEyOklzc3VlQ29tbWVudDUyOTE2NDUwNg==,30388627,2019-09-08T02:52:56Z,2019-09-08T02:52:56Z,NONE,"@shoyer Thanks. It's not datetime64 arrays, this is the result of `np.isnat(t)`:
```
  File ""/public/software/anaconda/anaconda3/envs/python36/lib/python3.6/site-packages/xarray-0.12.3-py3.6.egg/xarray/core/arithmetic.py"", line 69, in __array_ufunc__
    dask='allowed')
  File ""/public/software/anaconda/anaconda3/envs/python36/lib/python3.6/site-packages/xarray-0.12.3-py3.6.egg/xarray/core/computation.py"", line 969, in apply_ufunc
    keep_attrs=keep_attrs)
  File ""/public/software/anaconda/anaconda3/envs/python36/lib/python3.6/site-packages/xarray-0.12.3-py3.6.egg/xarray/core/computation.py"", line 217, in apply_dataarray_vfunc
    result_var = func(*data_vars)
  File ""/public/software/anaconda/anaconda3/envs/python36/lib/python3.6/site-packages/xarray-0.12.3-py3.6.egg/xarray/core/computation.py"", line 564, in apply_variable_ufunc
    result_data = func(*input_data)
TypeError: ufunc 'isnat' is only defined for datetime and timedelta.
```

I use `pd.isnull(t).all()` to check it, it works. Actually it's all nan.
There's something wrong with the nc file, I will contact the data center.
Thank you for all your help :) ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529164037,https://api.github.com/repos/pydata/xarray/issues/3290,529164037,MDEyOklzc3VlQ29tbWVudDUyOTE2NDAzNw==,1217238,2019-09-08T02:41:58Z,2019-09-08T02:41:58Z,MEMBER,"For datetime64 arrays, use np.isnat() instead of isnan.

On Sat, Sep 7, 2019 at 7:39 PM Xin Zhang <notifications@github.com> wrote:

> @keewis <https://github.com/keewis> I tried to using
> np.isnan(t.values).all() to check whether it's all nan. But, I got this
> error:
>
>     print (np.isnan(t.values).all())
> TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''
>
> This is the type of t.values: <class 'numpy.ndarray'>
>
> —
> You are receiving this because you were mentioned.
> Reply to this email directly, view it on GitHub
> <https://github.com/pydata/xarray/issues/3290?email_source=notifications&email_token=AAJJFVWLAIBI55TBPAXWLDLQIRQWHA5CNFSM4IUO4E7KYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOD6FGMMY#issuecomment-529163827>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AAJJFVWBG7JHMQIYCYB3IJ3QIRQWHANCNFSM4IUO4E7A>
> .
>
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529163827,https://api.github.com/repos/pydata/xarray/issues/3290,529163827,MDEyOklzc3VlQ29tbWVudDUyOTE2MzgyNw==,30388627,2019-09-08T02:39:30Z,2019-09-08T02:39:30Z,NONE,"@keewis I tried to using `np.isnan(t.values).all()` to check whether it's all nan. But, I got this error:
```
    print (np.isnan(t.values).all())
TypeError: ufunc 'isnan' not supported for the input types, and the inputs could not be safely coerced to any supported types according to the casting rule ''safe''
```
This is the type of `t.values`: `<class 'numpy.ndarray'>`","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529163295,https://api.github.com/repos/pydata/xarray/issues/3290,529163295,MDEyOklzc3VlQ29tbWVudDUyOTE2MzI5NQ==,14808389,2019-09-08T02:27:23Z,2019-09-08T02:27:23Z,MEMBER,do you actually have any non-nan values in your array? From what I understand of how nanops work is that `AlwaysGreaterThan` should only be returned by `min()` if there are no non-nan values.,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529163060,https://api.github.com/repos/pydata/xarray/issues/3290,529163060,MDEyOklzc3VlQ29tbWVudDUyOTE2MzA2MA==,30388627,2019-09-08T02:22:01Z,2019-09-08T02:22:01Z,NONE,"@shoyer Thank. It works now. But, I get another question.
This is the result of `t = ds['time_utc']`:
```
<xarray.DataArray 'time_utc' (time: 1, scanline: 357, ground_pixel: 450)>
array([[[nan, nan, ..., nan, nan],
        [nan, nan, ..., nan, nan],
        ...,
        [nan, nan, ..., nan, nan],
        [nan, nan, ..., nan, nan]]], dtype=object)
Coordinates:
  * scanline      (scanline) float64 1.0 2.0 3.0 4.0 ... 354.0 355.0 356.0 357.0
  * ground_pixel  (ground_pixel) float64 1.0 2.0 3.0 4.0 ... 448.0 449.0 450.0
  * time          (time) datetime64[ns] 2019-08-25
Attributes:
    long_name:  Time of observation as ISO 8601 date-time string
```
If I want to get the minimum value by `t.min(skipna=True)`, I get the strange type:
```
<xarray.DataArray 'time_utc' ()>
array(<xarray.core.dtypes.AlwaysGreaterThan object at 0x7f96ac188550>,
      dtype=object)
```
Can't convert it to string by `str(t.min(skipna=True))`.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529152703,https://api.github.com/repos/pydata/xarray/issues/3290,529152703,MDEyOklzc3VlQ29tbWVudDUyOTE1MjcwMw==,1217238,2019-09-07T22:43:48Z,2019-09-07T22:44:18Z,MEMBER,"I think this may have been fixed by https://github.com/pydata/xarray/pull/2924 (which removed the line with `dtypes.fill_value(value.dtype) if valid_count == 0 else data`)

Can you try upgrading to xarray 0.12.3?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529091168,https://api.github.com/repos/pydata/xarray/issues/3290,529091168,MDEyOklzc3VlQ29tbWVudDUyOTA5MTE2OA==,30388627,2019-09-07T09:33:32Z,2019-09-07T09:33:32Z,NONE,"@max-sixty  Actually, I'm using numpy = 1.13.1 and I need skipna= True. Don't understand the error it shows.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787
https://github.com/pydata/xarray/issues/3290#issuecomment-529083217,https://api.github.com/repos/pydata/xarray/issues/3290,529083217,MDEyOklzc3VlQ29tbWVudDUyOTA4MzIxNw==,5635139,2019-09-07T07:40:32Z,2019-09-07T07:40:32Z,MEMBER,"Thanks for the issue @zxdawn . Did you try doing this?

> NotImplementedError: min is not available with skipna=False with the installed version of numpy; upgrade to numpy 1.12","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,490593787