FIX: raise clear ValueError when no ECG events found in create_ecg_ep… (#13771)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Daniel McCloy <dan@mccloy.info>

Author: 3 people

doc/changes/dev/13771.bugfix.rst

@@ -0,0 +1 @@
+Clearer error message when no ECG events are found in :func:`~mne.preprocessing.find_ecg_events`, by :newcontrib:`Hansuja Budhiraja`.

mne/preprocessing/ecg.py

@@ -278,8 +278,7 @@ def find_ecg_events(
     if ecg_events.size > 0:
         ecg_events = remap[ecg_events]
     else:
-        ecg_events = np.array([])
-
+        ecg_events = np.array([], int)
     n_events = len(ecg_events)
     duration_sec = len(ecg) / raw.info["sfreq"] - tstart
     duration_min = duration_sec / 60.0
@@ -430,6 +429,9 @@ def create_ecg_epochs(
         reject_by_annotation=reject_by_annotation,
     )
 
+    if len(events) == 0:
+        raise ValueError("No ECG events could be found.")
+
     picks = _picks_to_idx(raw.info, picks, "all", exclude=())
 
     # create epochs around ECG events and baseline (important)

mne/preprocessing/tests/test_ecg.py

@@ -118,6 +118,10 @@ def test_find_ecg():
     assert average_pulse == 0
     assert np.allclose(ecg, np.zeros_like(ecg))
 
+    # Test that create_ecg_epochs raises clear error when no ECG events found
+    with pytest.raises(ValueError, match="No ECG events could be found."):
+        create_ecg_epochs(raw, ch_name=raw.ch_names[ecg_idx])
+
     # Needs MEG
     with pytest.raises(ValueError, match="Generating an artificial"):
         find_ecg_events(read_raw_fif(raw_fname, preload=False).pick("eeg"))