function nextstage(directory, inputfile)

% read data
        disp('reading file');
        directory = strcat(directory, '\');
        [timemat, posmat] = gdf2mat(strcat(directory, inputfile), [], [], [], 'all');
        
% extract screen

% convert coordinates

% output file
        outputfile = strcat(directory, 'nextstage.gdf');
        disp(['writing file ' outputfile]);
        
return