How can I rename all columns in a table using a cell array?

I am trying to rename columns in a table. There are 11904 columns, so I am using a cell array for the variable names. However, I get the error:

The VariableNames property must be a cell array, with each element containing one nonempty string.

I do not know how to convert the cell array into something that can be used in the NewTable.Properties.VariableNames function. Thanks!

Here is my code:

disp('Converting .txt measurements to .csv...')
dirs = dir(pathname_meas);

for i = 1:length(dir(pathname_meas));    
    if strfind(dirs(i).name,'All.txt');
        datas = readtable(dirs(i).name,'delimiter','\t');
        ncols = (height(datas)/std_erp_count);
        channels=[64,32];
        counter=1;
        bin_num=1;
        col_labs=cell(1, ncols);
        for j = 1:(ncols)
            if counter < channels(2-ch64)
                col_labs{j}=strcat(datas(j,'chlabel').chlabel,'_',int2str((bin_num)));
                counter=counter+1;
            else
                col_labs{j}=strcat(datas(j,'chlabel').chlabel,'_',int2str((bin_num)));
                counter = 1;
                bin_num=bin_num+1;
            end
        end
    % create new matrix - participant x electrode
    transposed_column = transpose(table2cell(datas(:,'value')));
    newTable = reshape(transposed_column,ncols, std_erp_count);
    newTable = array2table(transpose(newTable));
    % Change column names
    for new_column_names = 1:length(col_labs)
        newTable.Properties.VariableNames(new_column_names)=col_labs{new_column_names};
    end 
%     newTable.Properties.VariableNames=col_labs;
    disp('Writing measurements to .csv file...')
    writetable(newTable,[pathname_meas strcat(dirs(i).name(1:length(dirs(i).name)-3),'csv')],'Delimiter',',');
    end

[per isakson]

An example from the doc:

T = table([10;20],{'M';'F'});
T.Properties.VariableNames = {'Age','Gender'}

"cell array for the variable names" I see no reason to the error you get.

What does

whos your_cell_array
iscellstr( your_cell_array )

output?

[David Bridges]

Thanks, here are responses - Note, I have changed number of columns to 3520:

>>whos col_labs
    Name          Size               Bytes  Class    Attributes

      col_labs      1x3520            826210  cell  

>> iscellstr(col_labs)
ans =
     0

I realised that it works if I do the following, but perhaps there is a better way:

for new_column_names = 1:length(col_labs)
 newTable.Properties.VariableNames(new_column_names)=col_labs{new_column_names};
end

[per isakson]

>> iscellstr(col_labs)
ans =
     0

needs to show 1, i.e true. The reason was (you have now edit the code) that col_labs was a cell array of cells of a string (as @Jan writes in his answer.)

Answer 1

[Jan]

col_labs{i}={strcat(char(table_columns_1(i)),'_',int2str((counter)))};

creates a cell, which contains cell strings. Better:

col_labs{i} = strcat(table_columns_1{i}, '_', int2str((counter)));

Note that you have 2 nested "for i" loops:

for i = 1:length(dir(pathname_meas));
  ...
  for i = 1:(11904)

This is at least confusing.

Try this:

col_labs = cell(1, 11904);  % Pre-allocate!!!
for iFile = 1:length(dirs)
  if strfind(dirs(i).name, 'All.txt');
    datas = readtable(dirs(i).name, 'delimiter', '\t');
    table_columns_1 = table2cell(datas(:, 'chlabel'));
    counter = 1;   % Inside the loop?!
    for k = 1:11904
      count       = rem(k - 1, 64) + 1;
      col_labs{k} = strcat(table_columns_1{k}), '_', int2str(counter));
    end
  ...

[David Bridges]

Thanks, I have updated the code with some of your suggestions. I realised I made some errors re: 2 "i"s in nested loops and had to make some other changes. Although, even with your changes to col_lab, it still does not work - perhaps as the cell array is not a cell string? - please see above question. Also, it works if you loop through the cell array (see new code), but perhaps could be more efficient without a loop.