how to verify that Brainflow markers have been inserted

dyCrane · February 2023

Hello everyone,

I'm new to openBCI and in recent days, I'm doing some simple experiments to make me more familiar with it. I simply use a CYTON board (8 channels) to collect a short piece of EEG data (the duration of this process is less than 20 seconds) and then run code samples introduced in the documentation of BrainFlow (https://brainflow.readthedocs.io/en/stable/Examples.html) to know what functions can I use on this equipment.

However, when I run the code sample of "Markers" (https://brainflow.readthedocs.io/en/stable/Examples.html#python-markers, the language I use is Python, and this code sample uses a function named "insert_marker"), though the code finishes successfully, I have no idea what happens on the data that I collect. I've tried to print out the shape of data before and after using this function, but there is no obvious fact to prove that the data have got some changes. (Maybe I should specify that the first step I do is collect the EEG data and get a record file in the format of .csv, then I use PLAYBACK_FILE_BOARD in my Python script to playback the file. I didn't add any markers when I record the EEG data, I just add markers using "insert_marker" function after the process of recording)

Now I feel doubtful about the differences between the EEG data processed with the "insert_marker" function or not. If markers do insert into the EEG data, how can I see them in a visual way after running the code sample I mentioned above?

What's more, If I add markers while recording the EEG data, will markers appear in the widget of "Time Series" in openBCI GUI? Or the values of the markers can be seen in the record file (If so, in which column)? Besides, after reading some posts about inserting markers into data, I know a mode called "marker mode", only can I see markers when I use this mode of openBCI (If so, how can I enter this mode using GUI)?

Thanks for your attention and looking forward to your suggestions!

wjcroft · February 2023

Crane, hi.

Best way to get answers on Brainflow features, such as the markers, is to post on the Brainflow Slack. Signup here:

https://brainflow.org/

I don't believe that the GUI currently shows marker locations. But Andrey (Brainflow dev) would know how to retrieve them.

William

dyCrane · February 2023

Hi William,
thanks for your suggestions! I will try to post this question on the Brainflow Slack and comment back here if I get available progress.

dyCrane · February 2023

Hi, back with a solution with the advice of Andrey.

Now I feel doubtful about the differences between the EEG data processed with the "insert_marker" function or not. If markers do insert into the EEG data, how can I see them in a visual way after running the code sample I mentioned above?

If markers are inserted into the data, the values of the markers can be seen in the last column, which is the marker column of the return data or the record file (if save the file after inserting markers).

To see the markers, we can use the code shown below:

data = board.get_board_data()
marker_channel = BoardShim.get_marker_channel(board_id)
data_marker = data[marker_channel]

how to verify that Brainflow markers have been inserted

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