how to add new column in existing text file?

I want to add new column in text files as their file names. I have 12000 files and i want to update them with their numbers. kindly help me to write a code for them. The desired text files should be as shown

[Rik]

Ah, so you did post it as a separate question. Same question here: what have you tried so far? Try splitting a problem into solvable parts.

[MS11]

on the left is my input file and output file shown on the right. I add new column by using Excel but I have more than 12K files and I want to do the same with all of them with Matlab. can you write a code for this problem?

Answer 1

[Bhaskar R]

for ii = 1:12000 
    filename = [num2str(ii), '.txt'];   % your file names as 1, 2.. .txt
    mat = readmatrix(filename);    % get file data
    mat = [repmat(ii, size(mat, 1), 1), mat];   % append filename value to data
    writematrix(mat, filename, 'Delimiter',' ');    % write file with name
 end

Hope this works for you !!

[MS11]

I hope so but it shows this error

Error using readmatrix (line 146)

Unable to find or open '1.txt'. Check the path and filename or file permissions.

Error in add_column (line 6)

mat = readmatrix(filename); % get file data

[Rik]

You need to adapt the code to make sure it generates the path to your files.

[Walter Roberson]

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[MS11]

thank you so much @Rik, @Walter and special thanks to @bhaskar. It works now.

[Jonathon Klepatzki]

Hi @Rik,

I have a question. Let's say that I have a file or a series of files that's inputted into a table. I want to grab the year from the filename (e.g. temp_summary.05.month_year.txt), how can I adjust the code you suggested to do that and add it to a new column?

[Walter Roberson]

@Jonathon Klepatzki

filename = 'temp_summary.05.08_2011.txt';

%more general form
[~, basename] = fileparts(filename);
nameparts = regexp(basename, '\.', 'split');
dateparts = regexp(nameparts{end}, '_', 'split');
year_str = dateparts{end}

year_str = '2011'

%special case where the year is the last thing after _
[~, basename] = fileparts(filename);
dateparts = regexp(basename, '_', 'split');
year_str = dateparts{end}

year_str = '2011'

[Jonathon Klepatzki]

@Walter Roberson,

Thank you, it worked!