Indexing problem: Unable to use a value of type cell as an index

Hello,

I have collected EEG data from multiple participants and created an Excel table with the trials that I rejected. Now I want to remove the same trials from the stimuli data. The rejected trials are different for each subject and are categorised into three columns, corresponding to (rejected_p0, rejected_p1, rejected_p2).

For this I am using a for loop to load the stimuli data of each subject (downsamp_audio.mat) and replace the trials with an empty vector (downsamp_audio_rejctp1, [] ). My problem is with how to index the trials I want to remove. I want to get the trials from my excel table into a new structure (rejectrl.p1) and use that as an index inside the loop.

Is there a way to save the trials numbers in a vector or structure that can be used for indexing? And not as cell, since that doesn't work.

subject = ["subj1"; "subj2"; "subjx"]

%Read excel table containing the rejected trials for each subject, split
%into three columns (part0, part1, part2)
rejecTrials_all = table2struct(readtable('/TablewithTrialstobeRemoved.xlsx'), 'ToScalar', true);

%get rejected trials only from part1 into a separate structure 
rejectrl.p1 = rejctTrials_all.rejected_p1; 

% Run for loop and remove rejected trials from the stimuli files of each subject
for subj = 1:length(subjects)
       %load stimuli files
       load(fullfile(audioDIR, [subjects{subj} '_downsamp_audio.mat']), 'downsamp_audio'); 
       
    for i = 1:length(downsamp_audio)        
          downsamp_audio_rejctp1 = downsamp_audio;
          downsamp_audio_rejctp1(rejectrl(subj).p1) = []; %replace the bad trials with empty vector in the stimulus files
          %Here is where I get the ERROR  
    end
         save(fullfile(outDIR, [subjects{subj} '_downsamp_audio_rejctp1.mat']),'downsamp_audio_rejctp1', '-v7.3');
end

Would be thankful for any suggestions!

Answer 1

[Ayush]

Hi @Lea Kerciku,

To save the trials numbers in a vector you can use “cell2mat” function.

% Load the Excel table containing rejected trials
rejected_trials = xlsread('path_to_your_excel_file.xlsx');

% Extract the trial numbers for rejected_p1
rejected_p1 = rejected_trials(:, 2); % Assuming rejected_p1 is in the second column

% Convert the cell array to a numeric array
rejected_p1 = cell2mat(rejected_p1);

To read more about the “cell2mat” function kindly view the following documentation.

https://www.mathworks.com/help/matlab/ref/cell2mat.html?s_tid=doc_ta

Thank you.

Hope this helps!