fix #611

dascore/core/coordmanager.py

@@ -514,6 +514,9 @@ def disassociate_coord(self, *coord: str) -> Self:
 
         These coordinates will no longer be associated with a dimension in
         the coord manager but can still be retrieved.
+        If one of the provided names is a dimension, coordinates associated
+        with that dimension are dropped unless they are also explicitly listed
+        in ``coord``.
 
         Parameters
         ----------

dascore/transform/fourier.py

@@ -354,8 +354,9 @@ def _get_stft_dims(dim, dims, axis):
         time = dc.to_timedelta64(time)
     # Get new dimensions
     new_dims = list(_get_stft_dims(dim, patch.dims, axis))
-    # Make dict of coordinates and return coord manager.
-    coord_map = dict(patch.coords.coord_map)
+    # Match dft behavior by removing coords associated with transformed dim,
+    # while keeping the transformed dim itself as a non-dimensional coord.
+    coord_map = patch.coords.disassociate_coord(dim).get_coord_tuple_map()
     new_units = invert_quantity(coord.units)
     coord_map.update(
         {
@@ -431,6 +432,8 @@ def stft(
     - If an array is passed for taper_window that has a different length
       than specified in kwargs, artificial enriching of frequency resolution
       (equivalent to zero padding in time domain) can occur.
+    - Non-dimensional coordinates associated with transformed coordinates
+      are dropped in the output.
 
     See Also
     --------

docs/tutorial/transformations.qmd

@@ -70,3 +70,8 @@ inverse =  transformed.istft()
 
 transformed.abs().select(distance=0, samples=True).squeeze().viz.waterfall();
 ```
+
+:::{.callout-note}
+`stft` drops non-dimensional coordinates associated with the transformed
+dimension, matching `dft` behavior.
+:::

tests/test_transform/test_fourier.py

@@ -341,6 +341,19 @@ def test_none_for_overlap(self, random_patch):
         out = random_patch.stft(time=1, overlap=None)
         assert isinstance(out, dc.Patch)
 
+    def test_non_dim_coord_associated_with_transform(self):
+        """See #611."""
+        patch = dc.get_example_patch("random_das", shape=(10, 200))
+        aux_time = np.arange(len(patch.get_coord("time")), dtype=float)
+        aux_dist = np.arange(len(patch.get_coord("distance")), dtype=float)
+        patch = patch.update_coords(
+            aux_time=("time", aux_time),
+            aux_dist=("distance", aux_dist),
+        )
+        out = patch.stft(time=0.1)
+        assert "aux_time" not in out.coords.coord_map
+        assert "aux_dist" in out.coords.coord_map
+
 
 class TestInverseSTFT:
     """Tests for the inverse short-time Fourier transform."""