FIX : set event onset to first_samp not 0 with initial_value is True (m…

…ne-tools#10289)

* FIX : set event onset to first_samp not 0 with initial_value is True

* update what's new

* pep8

doc/changes/latest.inc

@@ -177,6 +177,8 @@ Bugs
 
 - :func:`mne.read_trans` now correctly expands ``~`` in the provided path to the user's home directory (:gh:`10265`, by `Richard Höchenberger`_)
 
+- :func:`mne.find_events` now uses ``first_samp`` and not ``0`` for initial event when using ``initial_value`` (:gh:`10289`, by `Alex Gramfort`_)
+
 API changes
 ~~~~~~~~~~~
 - ``mne.Info.pick_channels`` has been deprecated. Use ``inst.pick_channels`` to pick channels from :class:`~mne.io.Raw`, :class:`~mne.Epochs`, and :class:`~mne.Evoked`. Use :func:`mne.pick_info` to pick channels from :class:`mne.Info` (:gh:`10039` by `Mathieu Scheltienne`_)

mne/event.py

@@ -474,7 +474,8 @@ def _find_events(data, first_samp, verbose=None, output='onset',
     initial_value = data[0, 0]
     if initial_value != 0:
         if initial_event:
-            events = np.insert(events, 0, [0, 0, initial_value], axis=0)
+            events = np.insert(
+                events, 0, [first_samp, 0, initial_value], axis=0)
         else:
             logger.info('Trigger channel has a non-zero initial value of {} '
                         '(consider using initial_event=True to detect this '

mne/tests/test_event.py

@@ -381,12 +381,12 @@ def test_find_events():
     # test initial_event argument
     info = create_info(['MYSTI'], 1000, 'stim')
     data = np.zeros((1, 1000))
-    raw = RawArray(data, info)
+    raw = RawArray(data, info, first_samp=7)
     data[0, :10] = 100
     data[0, 30:40] = 200
-    assert_array_equal(find_events(raw, 'MYSTI'), [[30, 0, 200]])
+    assert_array_equal(find_events(raw, 'MYSTI'), [[37, 0, 200]])
     assert_array_equal(find_events(raw, 'MYSTI', initial_event=True),
-                       [[0, 0, 100], [30, 0, 200]])
+                       [[7, 0, 100], [37, 0, 200]])
 
     # test error message for raw without stim channels
     raw = read_raw_fif(raw_fname, preload=True)