added rewrite_coords accessor (#308)

* added rewrite_coords accessor

* update tests

* update docstrings

* update docstrings

* update whats new

* update whats new

cordex/accessor.py

@@ -5,6 +5,7 @@
 
 # from .utils import _get_info, _guess_domain
 from .tables import domains
+from .domain import rewrite_coords
 
 IDS = ["domain_id", "CORDEX_domain"]
 
@@ -91,12 +92,22 @@ def __init__(self, xarray_obj):
 
     @property
     def domain_id(self, guess=True):
-        """Returns the domain_id.
+        """
+        Returns the domain_id.
 
         This property will return the ``CORDEX_domain`` or ``domain_id`` global
         attribute if present. If none of those attributes are found, the
         domain information will be guessed.
 
+        Parameters
+        ----------
+        guess : bool, optional
+            If True, the domain information will be guessed if not found. Default is True.
+
+        Returns
+        -------
+        str
+            The domain_id.
         """
         if self._domain_id is None:
             self._domain_id = _get_domain_id(self._obj)
@@ -106,37 +117,44 @@ def domain_id(self, guess=True):
 
     @property
     def grid_mapping(self):
-        """Returns the grid_mapping variable."""
+        """
+        Returns the grid_mapping variable.
+
+        Returns
+        -------
+        xarray.DataArray
+            The grid_mapping variable from the xarray object.
+        """
         return self._obj.cf["grid_mapping"]
 
     def info(self):
-        """Return domain info in CORDEX format.
+        """
+        Return domain info in CORDEX format.
 
         The function returns a dictionary containing domain
         information in the format of the CORDEX archive specifications.
 
         Returns
         -------
-        domain info : dict
+        dict
             A dictionary that contains domain information.
-
         """
         if self._info is None:
             self._info = _get_info(self._obj)
         return self._info
 
     def guess(self):
-        """Guess which domain this could be.
+        """
+        Guess which domain this could be.
 
-        Compares the coordinate axis information to known the
+        Compares the coordinate axis information to known
         coordinates of known CORDEX domains to guess the
         ``domain_id``.
 
         Returns
         -------
-        domain info : dict
-            A dictionary that contains domain information.
-
+        dict
+            A dictionary containing the guessed domain information.
         """
         if self._guess is None:
             self._guess = _guess_domain(self._obj)
@@ -209,6 +227,56 @@ def map(self, projection=None):
         return ax
         # ax.set_title(CORDEX_domain)
 
+    def rewrite_coords(
+        self,
+        coords="xy",
+        bounds=False,
+        domain_id=None,
+        mip_era="CMIP5",
+        method="nearest",
+    ):
+        """
+        Rewrite coordinates in a dataset.
+
+        This function ensures that the coordinates in a dataset are consistent and can be
+        compared to other datasets. It can reindex the dataset based on specified coordinates
+        or domain information while trying to keep the original coordinate attributes.
+
+        Parameters
+        ----------
+        coords : str, optional
+            Specifies which coordinates to rewrite. Options are:
+            - "xy": Rewrite only the X and Y coordinates.
+            - "lonlat": Rewrite only the longitude and latitude coordinates.
+            - "all": Rewrite both X, Y, longitude, and latitude coordinates.
+            Default is "xy". If longitude and latitude coordinates are not present in the dataset, they will be added.
+            Rewriting longitude and latitude coordinates is only possible if the dataset contains a grid mapping variable.
+        bounds : bool, optional
+            If True, the function will also handle the bounds of the coordinates. If the dataset already has bounds,
+            they will be updated while preserving attributes and shape. If not, the bounds will be assigned.
+        domain_id : str, optional
+            The domain identifier used to obtain grid information. If not provided, the function will attempt
+            to use the domain_id attribute from the dataset.
+        mip_era : str, optional
+            The MIP era (e.g., "CMIP5", "CMIP6") used to determine coordinate attributes. Default is "CMIP5".
+            Only used if the dataset does not already contain coordinate attributes.
+        method : str, optional
+            The method used for reindexing the X and Y axis. Options include "nearest", "linear", etc. Default is "nearest".
+
+        Returns
+        -------
+        ds : xr.Dataset
+            The dataset with rewritten coordinates.
+        """
+        return rewrite_coords(
+            self._obj,
+            coords=coords,
+            bounds=bounds,
+            domain_id=domain_id,
+            mip_era=mip_era,
+            method=method,
+        )
+
 
 @xr.register_dataset_accessor("cx")
 class CordexDatasetAccessor(CordexAccessor):

docs/api.rst

@@ -108,3 +108,4 @@ Methods
     Dataset.cx.info
     Dataset.cx.guess
     Dataset.cx.map
+    Dataset.cx.rewrite_coords

docs/whats_new.rst

@@ -6,19 +6,30 @@ What's new
 v0.10.0 (Unreleased)
 --------------------
 
-New function  :py:meth:`cordex.rewrite_coords` that rewrites coordinates (X and Y axes and transformed coordinates) in a dataset to correct
+New function  :py:meth:`rewrite_coords` that rewrites coordinates (X and Y axes and transformed coordinates) in a dataset to correct
 rounding errors. This version drops python3.8 support.
 
 New Features
 ~~~~~~~~~~~~
 
-- New function :py:meth:`cordex.rewrite_coords` (:pull:`306`, :pull:`307`).
+- New function :py:meth:`rewrite_coords` (:pull:`306`, :pull:`307`). The function is also available as accessor function.
+
+Internal Changes
+~~~~~~~~~~~~~~~~
+
+- Update of API documentation in accessor (:pull:`308`).
 
 Breaking Changes
 ~~~~~~~~~~~~~~~~
 
 - Drop python3.8 support (:pull:`306`).
 
+Deprecations
+~~~~~~~~~~~~
+
+- :py:meth:`preprocessing.replace_coords` is deprecated in favour of :py:meth:`rewrite_coords`.
+
+
 v0.9.0 (18 November 2024)
 -------------------------
 

tests/test_accessor.py

@@ -1,5 +1,6 @@
 import pytest
 import xarray as xr
+import numpy as np
 
 import cordex as cx
 from cordex.accessor import CordexDataArrayAccessor, CordexDatasetAccessor  # noqa
@@ -33,3 +34,25 @@ def test_guess_info(domain_id):
 def test_dataset_guess(filename):
     ds = cx.tutorial.open_dataset(filename)
     assert ds.cx.guess() == cx.domain_info(ds.cx.domain_id)
+
+
+@pytest.mark.parametrize("domain_id", ["EUR-11", "EUR-44", "SAM-44", "AFR-22"])
+def test_rewrite_coords(domain_id):
+    # Create a sample dataset
+    grid = cx.domain(domain_id)
+
+    # Create typical coordinate precision issue by adding random noise
+    rlon_noise = np.random.randn(*grid.rlon.shape) * np.finfo("float32").eps
+    rlat_noise = np.random.randn(*grid.rlat.shape) * np.finfo("float32").eps
+    # lon_noise = np.random.randn(*grid.lon.shape) * np.finfo("float32").eps
+    # lat_noise = np.random.randn(*grid.lat.shape) * np.finfo("float32").eps
+
+    # Call the rewrite_coords function for "xy" coordinates
+    grid_noise = grid.assign_coords(
+        rlon=grid.rlon + rlon_noise, rlat=grid.rlat + rlat_noise
+    )
+    rewritten_data = grid_noise.cx.rewrite_coords(coords="xy")
+
+    np.testing.assert_array_equal(rewritten_data.rlon, grid.rlon)
+    np.testing.assert_array_equal(rewritten_data.rlat, grid.rlat)
+    xr.testing.assert_identical(rewritten_data, grid)