How to replace numbers on a particular line from text file?

Hallo, Thanks for reading!

As an example, I have the following text file (the line number does not exist on the real text file).

1 ((SUBWALL :N "Part 1" :T WALL-PART :D "Wall part_C")
2  (:PAR :N X :V 0.0)
3  (:PAR :N DX :V 1)
4  (:PAR :N DY :V 1)
5 ((SUBWALL :N "Part 1" :T WALL-PART :D "Wall part_WN")
6  (:PAR :N X :V 0.0)
7  (:PAR :N DX :V 0.5)
8  (:PAR :N DY :V 0.5)

I want to replace the '0.0' from line 2 with '2.1'. The code I used as follows.

x = 2.1;
r_line =  '(:PAR :N X :V %.1f)';
r_bb = sprintf(r_line,x);

However, it is replacing both line 2 and 6. How can avoid this and only change the digits in line 2?

Answer 1

[Walter Roberson]

Use readlines() to read the text file and split into lines. Then index the cell array to make changes.

After fopen a new file and fprintf(fid, '%s\n', TheCell{:}) and fclose.

[Kazi Alam]

@Walter Roberson Do you know the reason for the following error?

lines = readlines("zone.txt");
Unrecognized function or variable 'readlines'.

[Walter Roberson]

Hmmmm... you could have a corrupt MATLAB.

Or... you could be using an old version of MATLAB and forgot to mention that and didn't think that it was important to fill out the Release field when doing so helps avoid exactly these kind of difficulties.

See

https://www.mathworks.com/matlabcentral/answers/877228-best-solution-to-finding-repeating-characters-on-a-line#comment_1636553