How do I add the filename of where the data came from into a new column in a for loop

I am using code very similar to the below code:

I have a folder with different amounts of txt documents with similar names such as 100_2022.txt, 101_2022.txt ect. I take all those txt documents and ultimately am creating one large table that has all the data encased in each document. I am trying to figure out how to add the file name of where that particalar set of data in the table came from into a new coloumn into the table

myFolder = 'C:\users\examples\documents'; 
if ~isdir(myFolder)
    errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
    uiwait(warndlg(errorMessage));
    return;
end
filePattern = fullfile(myFolder, '*.txt');
myFiles = dir(filePattern);
for k = 1:length(myFiles)
    baseFileName = myFiles(k).name;
    fullFileName = fullfile(myFolder, baseFileName);
    fprintf(1, 'Now reading %s\n', fullFileName);
    x{k} = readtable(fullfilename)
    newtable =  vertcat(x{:});
end

Answer 1

[Voss]

myFolder = pwd();%'C:\users\examples\documents'; 
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
filePattern = fullfile(myFolder, '*.txt');
myFiles = dir(filePattern);
x = cell(1,numel(myFiles)); % pre-allocate cell array x
for k = 1:numel(myFiles)
  baseFileName = myFiles(k).name;
  fullFileName = fullfile(myFolder, baseFileName);
  fprintf(1, 'Now reading %s\n', fullFileName);
  x{k} = readtable(fullFileName); % use correct variable name "fullFileName" not "fullfilename"
  x{k}.SourceFile = repmat({fullFileName},size(x{k},1),1); % add SourceFile column in table x{k}
end

Now reading /users/mss.system.ejsX5t/sample1.txt
Now reading /users/mss.system.ejsX5t/sample2.txt
Now reading /users/mss.system.ejsX5t/sample3.txt

newtable = vertcat(x{:}) % vertcat all x once after the loop

newtable = 6×4 table
    Var1    Var2    Var3                   SourceFile               
    ____    ____    ____    ________________________________________

      1       2       3     {'/users/mss.system.ejsX5t/sample1.txt'}
      4       5       6     {'/users/mss.system.ejsX5t/sample1.txt'}
      7       8       9     {'/users/mss.system.ejsX5t/sample2.txt'}
     10      11      12     {'/users/mss.system.ejsX5t/sample2.txt'}
     13      14      15     {'/users/mss.system.ejsX5t/sample2.txt'}
     13      14      15     {'/users/mss.system.ejsX5t/sample3.txt'}