Allow concatenating BaseRaw objects

doc/changes/devel/13263.newfeature.rst

@@ -0,0 +1 @@
+It is now possible to concatenate raw objects with :func:`mne.concatenate_raws` as long as they inherit from :class:`~mne.io.BaseRaw`, even if their specific types differ (e.g., :class:`~mne.io.Raw` and :class:`~mne.io.RawArray`), by `Clemens Brunner`_.

mne/io/base.py

@@ -3104,8 +3104,9 @@ def _write_raw_buffer(fid, buf, cals, fmt):
 def _check_raw_compatibility(raw):
     """Ensure all instances of Raw have compatible parameters."""
     for ri in range(1, len(raw)):
-        if not isinstance(raw[ri], type(raw[0])):
-            raise ValueError(f"raw[{ri}] type must match")
+        if not isinstance(raw[ri], BaseRaw):
+            if type(raw[ri]) is not type(raw[0]):
+                raise ValueError(f"raw[{ri}] type must match")
         for key in ("nchan", "sfreq"):
             a, b = raw[ri].info[key], raw[0].info[key]
             if a != b:

mne/io/fiff/tests/test_raw_fiff.py

@@ -487,6 +487,22 @@ def test_concatenate_raws_order():
     assert np.all(ch0 == 0)
 
 
+def test_concatenate_raws_different_subtypes(tmp_path):
+    """Test concatenating raws with different subtypes."""
+    sfreq = 100.0
+    ch_names = ["EEG 001", "EEG 002"]
+    ch_types = ["eeg"] * 2
+    info = create_info(ch_names=ch_names, sfreq=sfreq, ch_types=ch_types)
+    data = np.random.randn(len(ch_names), 1000)
+
+    raw_array = RawArray(data, info)
+    raw_array.save(tmp_path / "temp_raw.fif", overwrite=True)
+    raw_fiff = read_raw_fif(tmp_path / "temp_raw.fif", preload=True)
+
+    with pytest.warns(RuntimeWarning, match="raw files do not all have the same"):
+        concatenate_raws([raw_fiff, raw_array])
+
+
 @testing.requires_testing_data
 @pytest.mark.parametrize(
     "mod",