Convert grand average file generated by mipgav4 into multiple csv files. Please note that you will also need the `csvwrite_with_headers` (if you don't already have it). It can be found here: http://www.mathworks.com/matlabcentral/fileexchange/29933-csv-with-column-headers/content/csvwrite_with_headers.m.

write_gav2csv.m

function write_gav2csv(infile, outprefix, smoothOn)
%     WRITE_GAV2CSV   Write the grand-average file as a CSV
%         write_gav2csv(infile, outfile)
%     
%     infile : Input grand average file name (e.g., 'myfile.gav')
%     outprefix : Prefix to output (e.g., 'myfile'). A separate file will be created corresponding to each bin.
%     smoothOn : 0 means no smoothing. 1 [default] = single smoothing. 2 = double smoothing, etc.
%
%     Created by Zarrar Shehzad on 2015-04-23.

  if nargin < 3
    smoothOn = 1;
  end
  
  % If don't want to use the whole function business
  % Then you can skip the above part and set the following three values given below
  % and then copy and paste all the code that follows
  %
  % infile = 'xxx'; % of course replace with your own stuff
  % outprefx = 'yyyy';
  % smoothOn = 2;

  % Read in the data
  fprintf('reading in data\n');
  hdr = EEGRead2(infile);
  dat = hdr.data;

  % Get the time-points
  tpts = -hdr.onset:hdr.sampling:(hdr.nPoints*hdr.sampling-hdr.onset-1);

  % Smooth data (if asked)
  if smoothOn > 0
    fprintf('smoothing data\n');
    for so = 1:smoothOn
      for ibin = 1:size(dat,1)
        for ichan = 1:size(dat,2)
          dat(ibin,ichan,:) = smooth(tpts, dat(ibin,ichan,:));
        end
      end
    end
  end

  % Save the data by bin
  for ibin = 1:size(dat,1)
    binName = hdr.binNames{ibin};
    outfile = strcat(outprefix, '_', binName, '.csv');
    fprintf('saving %s\n', outfile);
    binDat  = squeeze(dat(ibin,:,:));
    binDat  = [tpts; binDat]';
    headers = [{'time'}; hdr.chanNames];
    csvwrite_with_headers(outfile, binDat, headers);
  end

end