interpolate: Support timedelta; fix datetime on xarray 2025.1.2

doc/whats-new.rst

@@ -7,6 +7,8 @@ What's New
 
 v0.7.0 (unreleased)
 -------------------
+- ``interpolate``: Added support for timedelta coordinates;
+  fixed support for datetime coordinates other than ``M8[ns]`` in xarray 2025.1.2.
 
 
 .. _whats-new.0.6.0:

pyproject.toml

@@ -70,12 +70,13 @@ filterwarnings = [
     "error",
     # FIXME these need to be fixed in xarray
     "ignore:__array_wrap__ must accept context and return:DeprecationWarning",
-    "ignore:__array__ implementation doesn't accept a copy keyword, so passing copy=False failed:DeprecationWarning",
     # FIXME these need to be looked at
     'ignore:.*will no longer be implicitly promoted:FutureWarning',
     'ignore:.*updating coordinate .* with a PandasMultiIndex would leave the multi-index level coordinates .* in an inconsistent state:FutureWarning',
-    # xarray vs. pandas upstream
+    # These have been fixed; still needed for Python 3.9 CI
+    "ignore:__array__ implementation doesn't accept a copy keyword, so passing copy=False failed:DeprecationWarning",
     'ignore:Converting non-nanosecond precision datetime:UserWarning',
+    'ignore:Converting non-nanosecond precision timedelta:UserWarning',
 ]
 
 [tool.coverage.report]

xarray_extras/interpolate.py

@@ -68,10 +68,12 @@ def splrep(a: xarray.DataArray, dim: Hashable, k: int = 3) -> xarray.Dataset:
     a = a.transpose(dim, *[d for d in a.dims if d != dim])
     x = a.coords[dim].values
 
-    if x.dtype.kind == "M":
+    if x.dtype.kind == "M":  # datetime
         # Same treatment will be applied to x_new.
         # Allow x_new.dtype==M8[D] and x.dtype==M8[ns], or vice versa
         x = x.astype("M8[ns]").astype(float)
+    elif x.dtype.kind == "m":  # timedelta
+        x = x.astype("m8[ns]").astype(float)
 
     t = kernels.make_interp_knots(x, k, check_finite=False)
     if k < 2:
@@ -181,15 +183,20 @@ def splev(
     if t.shape != (c.sizes[dim] + k + 1,):
         raise ValueError("Interpolated dimension has been sliced")
 
-    if x_new.dtype.kind == "M":
+    if x_new.dtype.kind == "M":  # datetime
         # Note that we're modifying the x_new values, not the x_new coords
-        # xarray datetime objects are always in ns
-        x_new = x_new.astype(float)
+        x_new = x_new.astype("M8[ns]").astype(float)
+    elif x_new.dtype.kind == "m":  # timedelta
+        x_new = x_new.astype("m8[ns]").astype(float)
 
     if extrapolate == "clip":
         x = tck.coords[dim].values
-        if x.dtype.kind == "M":
+
+        if x.dtype.kind == "M":  # datetime
             x = x.astype("M8[ns]").astype(float)
+        elif x.dtype.kind == "m":  # timedelta
+            x = x.astype("m8[ns]").astype(float)
+
         x_new = np.clip(x_new, x[0].tolist(), x[-1].tolist())
         extrapolate = False
 

xarray_extras/tests/test_interpolate.py

@@ -192,8 +192,8 @@ def test_nonfloat(x_dtype, x_new_dtype):
 
 
 @pytest.mark.filterwarnings("ignore:Converting non-nanosecond precision datetime ")
-@pytest.mark.parametrize("x_new_dtype", ["<M8[D]", "<M8[s]", "<M8[ns]"])
-@pytest.mark.parametrize("x_dtype", ["<M8[D]", "<M8[s]", "<M8[ns]"])
+@pytest.mark.parametrize("x_new_dtype", ["M8[D]", "M8[s]", "M8[ns]"])
+@pytest.mark.parametrize("x_dtype", ["M8[D]", "M8[s]", "M8[ns]"])
 def test_dates(x_dtype, x_new_dtype):
     """
     - Test mismatched date formats on x and x_new
@@ -202,15 +202,36 @@ def test_dates(x_dtype, x_new_dtype):
     y = DataArray(
         [10, 20],
         dims=["x"],
-        coords={"x": np.array(["2000-01-01", "2001-01-01"]).astype(x_dtype)},
+        coords={"x": np.array(["2000-01-01", "2001-01-01"], dtype=x_dtype)},
     )
-    x_new = np.array(["2000-04-20", "2002-07-28"]).astype(x_new_dtype)
-    expect = DataArray(
-        [13.00546448, 20.0], dims=["x"], coords={"x": x_new.astype("<M8[ns]")}
+    x_new = np.array(["2000-04-20", "2002-07-28"], dtype=x_new_dtype)
+    expect = DataArray([13.00546448, 20.0], dims=["x"], coords={"x": x_new})
+
+    tck = splrep(y, "x", k=1)
+    y_new = splev(x_new, tck, extrapolate="clip")
+    assert y_new.x.dtype == expect.x.dtype
+    assert_allclose(expect, y_new, atol=1e-6, rtol=0)
+
+
+@pytest.mark.filterwarnings("ignore:Converting non-nanosecond precision datetime ")
+@pytest.mark.parametrize("x_new_dtype", ["m8[D]", "m8[s]", "m8[ns]"])
+@pytest.mark.parametrize("x_dtype", ["m8[D]", "m8[s]", "m8[ns]"])
+def test_timedeltas(x_dtype, x_new_dtype):
+    """
+    - Test mismatched date formats on x and x_new
+    - Test clip extrapolation on test_dates
+    """
+    y = DataArray(
+        [10, 20],
+        dims=["x"],
+        coords={"x": np.array([30, 50], dtype="m8[D]").astype(x_dtype)},
     )
+    x_new = np.array([35, 45], dtype="m8[D]").astype(x_new_dtype)
+    expect = DataArray([12.5, 17.5], dims=["x"], coords={"x": x_new})
 
     tck = splrep(y, "x", k=1)
     y_new = splev(x_new, tck, extrapolate="clip")
+    assert y_new.x.dtype == expect.x.dtype
     assert_allclose(expect, y_new, atol=1e-6, rtol=0)