Modify a BrainVision EEG marker file.

remarker.m

% Open the old marker file
filename = 'oldFile.vmrk';
fileId = fopen(filename); 

% Open a new marker file for writing
newFilename = 'newFile.vmrk';
newFileId = fopen(newFilename,'w');

% Get a line from the old file
thisLine = fgets(fileId);

% Loop through each line of the old file
while ischar(thisLine)
    
    % If this line includes a marker, e.g. 'S  1' through 'S255'
    if ~isempty(regexp(thisLine, 'S  [1-9]|S [1-9][0-9]|S[1-2][0-9][0-9]', 'once'))
        
        [matchStart, matchEnd] = regexp(thisLine, 'S  [1-9]|S [1-9][0-9]|S[1-2][0-9][0-9]'); % Get start/end characters
        
        thisMarkerString = thisLine(matchStart + 1:matchEnd); % Get this marker's string
        thisMarker = str2double(thisMarkerString); % Convert to a number for modification 
        
        newMarker = thisMarker; % Modify marker as needed
       
        newMarkerString = sprintf('S%3d',newMarker); % Make a string for new marker
        thisLine(matchStart:matchEnd) = newMarkerString; % Modify line from original marker file
    end
    
    % Write to new file
    fwrite(newFileId,thisLine);
    
    % Get next line
    thisLine = fgets(fileId);
end

% Close old and new marker files
fclose(fileId);
fclose(newFileId);