Change nodata from rioxarray default to nan in pyramid_reproject (#110)

ndpyramid/core.py

@@ -4,6 +4,7 @@
 from collections import defaultdict
 
 import datatree as dt
+import numpy as np
 import xarray as xr
 
 from .common import Projection
@@ -131,12 +132,14 @@ def pyramid_reproject(
         dst_transform = projection_model.transform(dim=dim)
 
         def reproject(da, var):
-            return da.rio.reproject(
+            da.encoding['_FillValue'] = np.nan
+            da = da.rio.reproject(
                 projection_model._crs,
                 resampling=Resampling[resampling_dict[var]],
                 shape=(dim, dim),
                 transform=dst_transform,
             )
+            return da
 
         # create the data array for each level
         plevels[lkey] = xr.Dataset(attrs=ds.attrs)

tests/test_pyramids.py

@@ -28,13 +28,23 @@ def test_reprojected_pyramid(temperature, benchmark):
     pytest.importorskip('rioxarray')
     levels = 2
     temperature = temperature.rio.write_crs('EPSG:4326')
-    pyramid = benchmark(lambda: pyramid_reproject(temperature, levels=2))
+    pyramid = benchmark(lambda: pyramid_reproject(temperature, levels=levels))
     assert pyramid.ds.attrs['multiscales']
     assert len(pyramid.ds.attrs['multiscales'][0]['datasets']) == levels
     assert pyramid.ds.attrs['multiscales'][0]['datasets'][0]['crs'] == 'EPSG:3857'
     pyramid.to_zarr(MemoryStore())
 
 
+def test_reprojected_pyramid_fill(temperature, benchmark):
+    """
+    Test for https://github.com/carbonplan/ndpyramid/issues/93.
+    """
+    pytest.importorskip('rioxarray')
+    temperature = temperature.rio.write_crs('EPSG:4326')
+    pyramid = benchmark(lambda: pyramid_reproject(temperature, levels=1))
+    assert np.isnan(pyramid['0'].air.isel(time=0, x=0, y=0).values)
+
+
 @pytest.mark.parametrize('regridder_apply_kws', [None, {'keep_attrs': False}])
 def test_regridded_pyramid(temperature, regridder_apply_kws, benchmark):
     pytest.importorskip('xesmf')