wrap all strings in table that contain a delimiter with a quote character

quote_delim_table.m

function tableout = quote_delim_table(tablein, delimiter, varargin)
%% wrap all strings in table that contain a delimiter with a quote character
% SYNTAX
%   tableout = quote_delim_table(tablein, delimiter)
%   tableout = quote_delim_table(tablein, delimiter, quotechar)
%
% DESCRIPTION
%   tableout = quote_delim_table(tablein, delimiter) all character columns in
%   tablein, and wraps strings containing delimiter with a double quote ('"')
%
%   tableout = quote_delim_table(tablein, delimiter, quotechar) wraps all strings
%   with delimiter with the single character in quotechar
%
% NOTES
%   If the string contains the quote character, replace with double quotes and
%   also wrap the line in quotes
% EXAMPLES
%     t = cell2table([num2cell(1:3)', num2cell(6:8)', {'OK comment'; 'bad, comment'; 'Also "trouble"'}],...
%                    'VariableNames', {'x', 'y', 'notes'})
%     %     x    y         notes      
%     %     _    _    ________________
%     % 
%     %     1    6    'OK comment'    
%     %     2    7    'bad, comment'  
%     %     3    8    'Also "trouble"'
% 
%     writetable(t, 'bad.csv',...
%                'delimiter', ',')
%     % % File contents:
%     % x,y,notes
%     % 1,6,OK comment
%     % 2,7,bad, comment
%     % 3,8,Also "trouble"
% 
%     tin = readtable('bad.csv',...
%                     'delimiter', ',')
%     % causes an error! 
%     % Delimiter on line 2 confuses it
%     % Also, the trailing quote on last line would be cut off on read in
% 
%     tfixed = quote_delim_table(t, ',')
%     %     x    y           notes        
%     %     _    _    ____________________
%     % 
%     %     1    6    'OK comment'        
%     %     2    7    '"bad, comment"'    
%     %     3    8    '"Also ""trouble"""'
% 
%     writetable(tfixed, 'bad_fixed.csv',...
%                'delimiter', ',')
% 
%     tfin = readtable('bad_fixed.csv',...
%                      'delimiter', ',')
%     %     x    y         notes      
%     %     _    _    ________________
%     % 
%     %     1    6    'OK comment'    
%     %     2    7    'bad, comment'  
%     %     3    8    'Also "trouble"'
%% check
if ~ischar(delimiter) || length(delimiter) ~= 1
    error('quote_delim_table:DelimArg',...
        'Delimiter argument ''%s'' is invalid. Must be char of length 1', delimiter);
end
%% quote char
if ~isempty(varargin)
    if ischar(varargin{1}) && length(varargin) == 1
        quotechar = varargin{1};
    else
        error('quote_delim_table:QuoteArg',...
            'Quote argument ''%s'' is invalid. Must be char of length 1', varargin{1});
    end
else
    quotechar = '"';  % default
end

%% find char columns
tstruct = table2struct(tablein);
vnames = fieldnames(tstruct);
nv = length(vnames);

vchar = false(1, nv);  % is the variable a character?
for i = 1:nv
    if strcmp(class([tstruct.(vnames{i})]), 'char')  % warns, but ischar does not work here
        vchar(i) = true;
    end
end
vchar = find(vchar);
%% Apply quotes
nq = length(vchar);
for i = 1:nq
    col = table2cell(tablein(:, vchar(i)));
    
    % replace empty cell with empty string
    idx_empty = cellfun(@isempty, col);
    col(idx_empty) = {''};
    
    % replace quote character with double quote
    col = cellfun(@(x) strrep(x, quotechar, [quotechar, quotechar]), col,...
                  'uni', false);
    
    % look for delimiter, or quote, wrap in quote
    
    idx_delim = ~cellfun(@isempty, regexp(col, [',|', quotechar], 'once'));
    col(idx_delim) = cellfun(@(x) [quotechar, x, quotechar], col(idx_delim),...
                               'uni', false);
    tablein(:, vchar(i)) = col;
end
%% done
tableout = tablein;