string output in text-file without " " (quotation notes). MATLAB BUG? comma in string effects quotation notes in .txt-file

Hi guys!

I noticed something strange in MATLAB. Maybe anybody knows this problem.

I would like to write a string-vector into a .txt-file.

If my string-vector contains a comma "," so my .txt.file begins with an quotation mark and end with one "....."

But i need a .txt-file without quotation marks, only with the strings, which maybe contains commas...

example 1 without comma in string and so without quotation marks in .txt-file:

Name1 = "Walter";
Gewicht1 = 55;

testvektor(1,1) = "Walter hat " + " / Hunger "+"";
testvektor(2,1) = "Gewicht" + ": " + Gewicht1;

fid = fopen('Textdatei.txt','wt'); 
writematrix(testvektor,'Textdatei.txt',"FileType","text")
fclose(fid); 

Output example 1:

Walter hat  / Hunger 
Gewicht: 55

example 2 with comma in string and so with quotation marks in .txt-file:

Name1 = "Walter";
Gewicht1 = 55;

testvektor(1,1) = "Walter hat " + " / Hunger "+",";
testvektor(2,1) = "Gewicht" + ": " + Gewicht1;

fid = fopen('Textdatei.txt','wt'); 
writematrix(testvektor,'Textdatei.txt',"FileType","text")
fclose(fid); 

Output example 2:

"Walter hat  / Hunger "
"Gewicht: 55"

Thank you for helping guys!

Hope you know the issue!

Best regards,

Maxim

[Walter Roberson]

It is not advisable to fopen(), writematrix(), fclose(). writematrix() does not operate on a file identifier: it opens and closes the file as needed. The extra fopen() justs risks glitches, unnecessarily.

[Maxim Kindsvater]

Thanks Walter. Thats a good point!

Answer 1

[Voss]

You can use "QuoteStrings","none" in your call to writematrix() to avoid writing the double-quotes in either case:

Name1 = "Walter";
Gewicht1 = 55;

testvektor(1,1) = "Walter hat " + " / Hunger "+"";
testvektor(2,1) = "Gewicht" + ": " + Gewicht1;
testvektor

testvektor = 2×1 string array
    "Walter hat  / Hunger "
    "Gewicht: 55"

writematrix(testvektor,'Textdatei.txt',"FileType","text","QuoteStrings","none")
show_file_contents('Textdatei.txt');

Walter hat  / Hunger 
Gewicht: 55

testvektor(1,1) = "Walter hat " + " / Hunger "+",";
testvektor(2,1) = "Gewicht" + ": " + Gewicht1;
testvektor

testvektor = 2×1 string array
    "Walter hat  / Hunger ,"
    "Gewicht: 55"

writematrix(testvektor,'Textdatei.txt',"FileType","text","QuoteStrings","none")
show_file_contents('Textdatei.txt');

Walter hat  / Hunger ,
Gewicht: 55

Or you can use fprintf() instead of writematrix():

fid = fopen('Textdatei.txt','w');
fprintf(fid,'%s\n',testvektor);
fclose(fid);
show_file_contents('Textdatei.txt');

Walter hat  / Hunger ,
Gewicht: 55

function show_file_contents(fn)
fid = fopen(fn);
data = fread(fid,'*char').';
fclose(fid);
disp(data);
end

[Jan]

Exactly. In a comma separated text file, the occurence of one comma inside the strings would create an ambiguous file. To avoid this double quotes are added as default when commas are found.

This is a smart feature, which can be confusing. This is a typical effect of applying heuristics to guess, what the users wants.