xarray-返回满足某些条件的数据，而不必使用for循环

Question

I am working with multi-dimensional data da_criteria_1or0_hourly .

The data (variable) is either 1 or 0.

print(da_criteria_1or0_hourly)

Output:

<xarray.DataArray (time: 8760, latitude: 106, longitude: 193)>
dask.array<shape=(8760, 106, 193), dtype=int32, chunksize=(744, 106, 193)>
Coordinates:
  * latitude   (latitude) float32 -39.2 -39.149525 ... -33.950478 -33.9
  * longitude  (longitude) float32 140.8 140.84792 140.89584 ... 149.95209 150.0
  * time       (time) datetime64[ns] 2017-01-01 ... 2017-12-31T23:00:00

The data is as massive as 179212080.

I am unsure which method on xarray I should use to get a new xarray object that only return data which is 1 ( 0 can be assigned NaN or dropped).

I was trying to print out data for each coordinate using sel using FOR LOOP, but this was extremely slow. It could take forever.

for time_elem in da_criteria_1or0_hourly.coords['time'].values:
    for lat_elem in da_criteria_1or0_hourly.coords['latitude'].values:
        for lon_elem in da_criteria_1or0_hourly.coords['longitude'].values:
            val = da_criteria_1or0_hourly.sel(time=time_elem,latitude=lat_elem,longitude=lon_elem).values
            if (val == 1):
                print(time_elem, lat_elem, lon_elem, val)

Is there any better way to do it?

Answer 1

If I understood your problem correctly xarray.Dataset.where should be the way to go:

da_criteria_1or0_hourly.where(da_criteria_1or0_hourly == 1)

This will return a new xarray where every entry that was not 1 is now NaN.

Time comparison for a 50x50x50 xarray:

for loops: ~56.9456s

where : ~00.0020s