蟒蛇-xarray副本楠从一个DataArray中另一个

Question

在我的最后一个问题稍微修改 python-xarray copy mask from one DataArray to another

当我在另一个HS文件中读取它拿起属性valid_min：0，因此该文件与楠的阅读自动

f = xr.open_dataset('ww3.Hs.mask.nc') 
<xarray.DataArray 'hs' (time: 1, latitude: 81, longitude: 131)> 
array([[[ nan, nan, ..., nan, nan], 
    [ nan, nan, ..., nan, nan], 
    ..., 
    [ nan, 0. , ..., 0.422, nan], 
    [ nan, nan, ..., nan, nan]]]) 
Coordinates: 
* latitude (latitude) float32 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 ... 
* longitude (longitude) float32 -100.0 -99.0 -98.0 -97.0 -96.0 -95.0 ... 
* time  (time) datetime64[ns] 1983-01-30 
Attributes: 
long_name:  significant height of wind and swell waves 
standard_name: sea_surface_wave_significant_height 
globwave_name: significant_wave_height 
units:   m 
valid_min:  0 
valid_max:  32000 

我现在想知道如何拿起这个面具的另一个变量。我的语法的猜测是：

ws10_masked = ws10.where(hs == nan) 
NameError: name 'nan' is not defined 

ws10_masked = ws10.where(hs.isnull) 
# Does not give an error message but does not set any values in ws10 to nan 

ws10_masked = ws10.where(hs.isnull()) 
Traceback (most recent call last): 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site- 
packages/xarray/backends/netCDF4_.py", line 60, in __getitem__ 
data = getitem(self.get_array(), key) 
File "netCDF4/_netCDF4.pyx", line 3730, in 
netCDF4._netCDF4.Variable.__getitem__ (netCDF4/_netCDF4.c:39703) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site- 
packages/netCDF4/utils.py", line 391, in _out_array_shape 
c = count[..., i].ravel()[0] # All elements should be identical. 
IndexError: index 0 is out of bounds for axis 0 with size 0 

During handling of the above exception, another exception occurred: 

Traceback (most recent call last): 
File "paper_test.py", line 62, in <module> 
ws10_masked = ws10.where(hs.isnull()) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/common.py", line 637, in where 
out = outobj._where(outcond) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site- 
packages/xarray/core/dataarray.py", line 1541, in func 
if not reflexive 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/ops.py", line 191, in func 
return getattr(self, name)(*args, **kwargs) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 873, in where 
return self._where(cond) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 1141, in func 
self_data, other_data, dims = _broadcast_compat_data(self, other) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 1376, in _broadcast_compat_data 
self_data = new_self.data 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 267, in data 
return self.values 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 308, in values 
return _as_array_or_item(self._data) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/variable.py", line 184, in _as_array_or_item 
data = np.asarray(data) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/numpy/core/numeric.py", line 531, in asarray 
return array(a, dtype, copy=False, order=order) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/indexing.py", line 419, in __array__ 
self._ensure_cached() 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/indexing.py", line 416, in _ensure_cached 
self.array = np.asarray(self.array) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/numpy/core/numeric.py", line 531, in asarray 
return array(a, dtype, copy=False, order=order) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/indexing.py", line 400, in __array__ 
return np.asarray(self.array, dtype=dtype) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/numpy/core/numeric.py", line 531, in asarray 
return array(a, dtype, copy=False, order=order) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/indexing.py", line 375, in __array__ 
return np.asarray(array[self.key], dtype=None) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/conventions.py", line 363, in __getitem__ 
self.scale_factor, self.add_offset, self._dtype) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/conventions.py", line 59, in mask_and_scale 
values = np.array(array, dtype=dtype, copy=True) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/core/indexing.py", line 375, in __array__ 
return np.asarray(array[self.key], dtype=None) 
File "/nethome/rxb826/PYTHON3/myenv/lib/python3.6/site-packages/xarray/backends/netCDF4_.py", line 71, in __getitem__ 
raise IndexError(msg) 
IndexError: The indexing operation you are attempting to perform is not valid on netCDF4.Variable object. Try loading your data into memory first by calling .load(). 

干杯， 雷

Answer 1

DataArray.isnull()是一种方法，而不是一个性质，所以你需要调用它：

ws10_masked = ws10.where(hs.isnull())