MATLAB: How correctly use fprintf

fprintfMATLAB

Hi,
could someone explain me how to correctly use fprint?
I made this test
testA =[1;2;3];
testB =[4;5;6];
fid = fopen('test_t.txt','w');
for i = 1 :3
    fprintf(fid,'%d  %d \n',testA(i),testB(i));
end
fclose(fid);
I was hoping to find this result in the .txt file
1 4
2 5
3 6
In the .txt file I see this " 1 4 2 5 3 6". But is funny because now that I tried to copy and paste the content of the text file in this question, I got this
    1  4 
    2  5 
    3  6
Can someone explain me:
  1. what does it mean " %d" in fprintf and where I find the documentation about it?
  2. Why I see something in the .txt file that does not look like what I want, except when I do copy and paste….
Thanks

Best Answer

Textfile Newlines
Try adding 't' to the fopen permissions string:
fid = fopen('test_t.txt','wt');
It is because the Windows newline actually consists of two characters, and simply using '\n' is not enough for some windows programs. The easiest solution is to add the 't' option to fopen, which makes this change automatically (for both reading and writing files). You might like to do this for all text files. You can read more about this in the fopen documentation.
fprintf Format String
%d is explained in the fprintf documentation as printing an "Integer, signed", which means it prints the numeric value provided as base-10 numeric digits in the file.
The MATLAB documentation is actually quite easy to read and navigate, you should try practice browsing it and try some of the examples that it includes!
Bonus Simplified Code
Note that you can simplify your code by removing the loop, because fprintf also works with arrays (but remember that MATLAB is column-major!):
>> testA =[1;2;3];
>> testB =[4;5;6];
>> fid = fopen('test.txt','wt');
>> fprintf(fid,'%d %d\n',[testA,testB].')
>> fclose(fid)
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