How to add a column to an existing file?

Hi, I've been looking in other questions in how to add a new column to an existing file but none of the codes work or are either way too simple.

I'm attaching my test file and the column I would like to add to it.

A = [0.23;0.44;0.65;0.12];

Answer 1

[A. Sawas]

I belelive you are trying to add a column of A to the file so your new file will be like this:

%--Existing file --  -- A --
4	0.45	100	0.23
3	4.54	65	0.44
2	0.23	233	0.65
1	0.45	200	0.12

Here is the code that will insert the column and save it in a new file testfile00W.txt. Assuming that the number of rows in A matches the number of rows in the file:

fidR = fopen('testfile00.txt', 'r');
fidW = fopen('testfile00W.txt', 'w');
line_ex = fgetl(fidR);
i = 1;
while line_ex > 0
    fprintf(fidW,['%s\t%f' newline], line_ex, A(i));
    line_ex = fgetl(fidR);
    i = i + 1;
end
fclose(fidR);
fclose(fidW);

Answer 2

[dpb]

Text sequential files are, well, "sequential" You can't just add in the middle by either column or line/record.

data=importdata('testfile00.txt');
dlmwrite('testfile00.txt',[data A],'\t')

Results--

>> type testfile00.txt

4	0.45	100	0.23
3	4.54	65	0.44
2	0.23	233	0.65
1	0.45	200	0.12
>> 

NB: This does overwrite the existing file as your question requested. That is, of course, quite possibly very dangerous if you make any mistakes...always have backups!!! unless it is a trivial exercise to regenerate the original data.