MATLAB Structure as an MNE RAW object

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The first step is the hardest, which is figuring out where in the MATLAB struct the various bits of information are stored. Here are some guidelines:

  1. After reading your MATLAB struct into Python, figure out which of its entries contain what. I usually start with sorted(data) to show the top-level key names, then print the key values one by one (e.g., data['History'], data['ChannelType'], etc). In your file there is a record array stored in data['F'] and it will be particularly helpful for you to look at data['F'][0, 0].dtype to get its column names, and then go through each entry (e.g., data['F'][0, 0]['header'], etc) to continue figuring out what data is stored where. Repeat the process as you find more nested record arrays: data['F'][0, 0]['events'].dtype, data['F'][0, 0]['events']['times'], etc. For example, data['F'][0, 0]['events']['times'] has shape (1, 7) where each element is an embedded array; data['F'][0, 0]['events']['label'] also has shape (1, 7) so presumably the times arrays are the times at which each corresponding label occurred. As you figure things out, take “notes” by assigning parts of the struct to descriptive variable names, like:
event_labels = np.concatenate(data['F'][0, 0]['events']['label'][0]).tolist()
event_times = data['F'][0, 0]['events']['times'][0].tolist()

  1. Once you’ve figured out where in the struct the actual measured signals are, convert it to a NumPy Array with shape (n_channels, n_times). Usually it will be clear from the shape of the array (n_times will usually be much bigger than n_channels). If the axes are in the wrong order, transpose it.

  2. Using the sampling frequency, channel names, and channel types you discovered in your investigation of the struct, create the Info using mne.create_info() (see the tutorial linked below).

  3. Using the data array and the Info object, use mne.io.RawArray() to create the Raw.

There is a tutorial showing how to create our data structures: Creating MNE-Python data structures from scratch — MNE 0.24.1 documentation that covers steps 3 and 4 above. Step 1 is the most time-consuming part.

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