function fix_lut(fld,monkey)
% we use a LUT to store information about trials. this is created by
% converting the log structure to a table and adding some extra columns.
% however, apparently the log structure does't always have the same fields,
% but the LUT needs to have the same columns to be able to concatenate.
% this fucntion adds two empty columns, for stimonset and targonset, which
% apparently were added to the log structure halfway throughout recording. 
% also, TarChoice is sometimes a cell, but it doesn't have to be because
% it's only ever 1 value. 

datadir = fld.procdatadir;
datainfo = session_info();

fprintf('\n======================================================\n');
fprintf(['-- Running fix_lut for ' monkey ' --\n']);
fprintf('======================================================\n');

if strcmp(monkey,'M1')
    info = datainfo(1);
else 
    info = datainfo(2);
end
sessions = info.dates;

for sid = 1:length(sessions)
    % session info
    session = sessions{sid};
    q = strsplit(session,'_');
    cdate = q{2};
    block = str2num(q{3}(end-4));

    % load the data 
    session_id = [monkey '_' cdate '_' num2str(block)];
    sessiondir = fullfile(datadir, monkey, session_id);
    
    % load the data for this session for this channel
    load(fullfile(sessiondir, [session_id '_LUT.mat'])); % loads 'lut'
    
    % add nans for stimonset
    if ~sum(strcmp('StimOnset',lut.Properties.VariableNames))
        StimOnset = nan(size(lut,1),1);
        lut = addvars(lut,StimOnset,'After','RewValue');
    end
    
    % add nans for targonset
    if ~sum(strcmp('TargOnset',lut.Properties.VariableNames))
        TargOnset = nan(size(lut,1),1);
        lut = addvars(lut,TargOnset,'After','StimOnset');
    end
    
    % make TarChoice not be a cell
    if iscell(lut.TarChoice)
        qq = nan(size(lut,1),1);
        qq(cellfun('isempty',lut.TarChoice)==0,1) = cell2mat(lut.TarChoice);
        lut.TarChoice = qq;
    end 
    
    save(fullfile(sessiondir, [session_id '_LUT.mat']),'lut');
end