fix mask_ocean for 2D grids (#314)

* fix mask_ocean for 2D grids

* rename to coords

* CHANGELOG

CHANGELOG.rst

@@ -60,7 +60,9 @@ New Features
    - Added functions to stack regular lat-lon grids to 1D grids and unstack them again (`#217
      <https://github.com/MESMER-group/mesmer/pull/217>`_). By `Mathias Hauser`_.
    - Added functions to mask the ocean and Antarctica (`#219
-     <https://github.com/MESMER-group/mesmer/pull/219>`_). By `Mathias Hauser`_.
+   - Added functions to mask the ocean and Antarctica (
+     `#219 <https://github.com/MESMER-group/mesmer/pull/219>`_ and
+     `#314 <https://github.com/MESMER-group/mesmer/pull/314>`_). By `Mathias Hauser`_.
    - Added functions to calculate the weighted global mean
      (`#220 <https://github.com/MESMER-group/mesmer/pull/220>`_ and
      `#287 <https://github.com/MESMER-group/mesmer/pull/287>`_). By `Mathias Hauser`_.

mesmer/core/mask.py

@@ -5,13 +5,13 @@
 import mesmer
 
 
-def _where_if_dim(obj, cond, dims):
+def _where_if_coords(obj, cond, coords):
 
     # xarray applies where to all data_vars - even if they do not have the corresponding
     # dimensions - we don't want that https://github.com/pydata/xarray/issues/7027
 
     def _where(da):
-        if all(dim in da.dims for dim in dims):
+        if all(coord in da.coords for coord in coords):
             return da.where(cond)
         return da
 
@@ -71,7 +71,7 @@ def mask_ocean_fraction(data, threshold, *, x_coords="lon", y_coords="lat"):
     mask_bool = mask_fraction > threshold
 
     # only mask data_vars that have the coords
-    return _where_if_dim(data, mask_bool, [y_coords, x_coords])
+    return _where_if_coords(data, mask_bool, [y_coords, x_coords])
 
 
 def mask_ocean(data, *, x_coords="lon", y_coords="lat"):
@@ -106,7 +106,7 @@ def mask_ocean(data, *, x_coords="lon", y_coords="lat"):
     mask_bool = mask_bool.squeeze(drop=True)
 
     # only mask data_vars that have the coords
-    return _where_if_dim(data, mask_bool, [y_coords, x_coords])
+    return _where_if_coords(data, mask_bool, [y_coords, x_coords])
 
 
 def mask_antarctica(data, *, y_coords="lat"):
@@ -132,4 +132,4 @@ def mask_antarctica(data, *, y_coords="lat"):
     mask_bool = data[y_coords] >= -60
 
     # only mask if data has y_coords
-    return _where_if_dim(data, mask_bool, [y_coords])
+    return _where_if_coords(data, mask_bool, [y_coords])

tests/unit/test_mask.py

@@ -133,3 +133,27 @@ def test_mask_antarctiva_default(
 def test_mask_antarctiva(as_dataset, y_coords):
 
     _test_mask(mesmer.mask.mask_antarctica, as_dataset, y_coords=y_coords)
+
+
+def test_mask_ocean_2D_grid():
+
+    lon = lat = np.arange(0, 30)
+    LON, LAT = np.meshgrid(lon, lat)
+
+    dims = ("rlat", "rlon")
+
+    data = np.random.randn(*LON.shape)
+
+    data_2D_grid = xr.Dataset(
+        {"data": (dims, data)}, coords={"lon": (dims, LON), "lat": (dims, LAT)}
+    )
+
+    data_1D_grid = xr.Dataset(
+        {"data": (("lat", "lon"), data)}, coords={"lon": lon, "lat": lat}
+    )
+
+    result = mesmer.mask.mask_ocean(data_2D_grid)
+    expected = mesmer.mask.mask_ocean(data_1D_grid)
+
+    # the Datasets don't have equal coords but their arrays should be the same
+    np.testing.assert_equal(result.data.values, expected.data.values)