Adding vectorized indexing docs (#4711)

Co-authored-by: Mathias Hauser <[email protected]> Co-authored-by: Mathias Hauser <[email protected]>
pydata · Feb 16, 2021 · 2ab0666 · 2ab0666
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diff --git a/doc/indexing.rst b/doc/indexing.rst
@@ -395,6 +395,22 @@ These methods may also be applied to ``Dataset`` objects
     ds = da.to_dataset(name="bar")
     ds.isel(x=xr.DataArray([0, 1, 2], dims=["points"]))
 
+Vectorized indexing may be used to extract information from the nearest
+grid cells of interest, for example, the nearest climate model grid cells
+to a collection specified weather station latitudes and longitudes.
+
+.. ipython:: python
+
+    ds = xr.tutorial.open_dataset("air_temperature")
+
+    # Define target latitude and longitude (where weather stations might be)
+    target_lon = xr.DataArray([200, 201, 202, 205], dims="points")
+    target_lat = xr.DataArray([31, 41, 42, 42], dims="points")
+
+    # Retrieve data at the grid cells nearest to the target latitudes and longitudes
+    da = ds["air"].sel(lon=target_lon, lat=target_lat, method="nearest")
+    da
+
 .. tip::
 
   If you are lazily loading your data from disk, not every form of vectorized

diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py
@@ -1094,6 +1094,26 @@ def isel(
         --------
         Dataset.isel
         DataArray.sel
+
+        Examples
+        --------
+        >>> da = xr.DataArray(np.arange(25).reshape(5, 5), dims=("x", "y"))
+        >>> da
+        <xarray.DataArray (x: 5, y: 5)>
+        array([[ 0,  1,  2,  3,  4],
+               [ 5,  6,  7,  8,  9],
+               [10, 11, 12, 13, 14],
+               [15, 16, 17, 18, 19],
+               [20, 21, 22, 23, 24]])
+        Dimensions without coordinates: x, y
+
+        >>> tgt_x = xr.DataArray(np.arange(0, 5), dims="points")
+        >>> tgt_y = xr.DataArray(np.arange(0, 5), dims="points")
+        >>> da = da.isel(x=tgt_x, y=tgt_y)
+        >>> da
+        <xarray.DataArray (points: 5)>
+        array([ 0,  6, 12, 18, 24])
+        Dimensions without coordinates: points
         """
 
         indexers = either_dict_or_kwargs(indexers, indexers_kwargs, "isel")
@@ -1202,6 +1222,34 @@ def sel(
         Dataset.sel
         DataArray.isel
 
+        Examples
+        --------
+        >>> da = xr.DataArray(
+        ...     np.arange(25).reshape(5, 5),
+        ...     coords={"x": np.arange(5), "y": np.arange(5)},
+        ...     dims=("x", "y"),
+        ... )
+        >>> da
+        <xarray.DataArray (x: 5, y: 5)>
+        array([[ 0,  1,  2,  3,  4],
+               [ 5,  6,  7,  8,  9],
+               [10, 11, 12, 13, 14],
+               [15, 16, 17, 18, 19],
+               [20, 21, 22, 23, 24]])
+        Coordinates:
+          * x        (x) int64 0 1 2 3 4
+          * y        (y) int64 0 1 2 3 4
+
+        >>> tgt_x = xr.DataArray(np.linspace(0, 4, num=5), dims="points")
+        >>> tgt_y = xr.DataArray(np.linspace(0, 4, num=5), dims="points")
+        >>> da = da.sel(x=tgt_x, y=tgt_y, method="nearest")
+        >>> da
+        <xarray.DataArray (points: 5)>
+        array([ 0,  6, 12, 18, 24])
+        Coordinates:
+            x        (points) int64 0 1 2 3 4
+            y        (points) int64 0 1 2 3 4
+        Dimensions without coordinates: points
         """
         ds = self._to_temp_dataset().sel(
             indexers=indexers,