writing bin data to *.dat file

Hey everybody,

again I couldn't find the right solution and need your wise counsel ;)

I have a binary vector i.e. like this: x = rand(50,1)*7; x = fi(x,false,3,0) x = bin(x);

Now I want to write this to a dat file. I acutally thought I could use dlmwrite('test.dat', x, 'newline', 'pc') but if x = [101 ; 110 ; 001 ; 011 ; ...]

the test.dat file looks like this: 1,0,1 1,1,0 0,0,1 0,1,1 . . .

and not like I would like to have it: 101 110 001 011 . . .

Any idea how I can teach dlmwrite to neglect the commas while still using the newline parameter? Should I probably use some other function?

Beste regards and thanks in advance,

Lennart

Answer 1

[Star Strider]

I don’t have the Fixed Point Designer, so I’m relying on the documentation for bin. The bin function returns a character array, and the dlmwrite function writes only numeric data. So it would seem that you have to convert the string to double-precision numeric, and use the 'precision' name-value pair argument.

See if this does what you want:

x = ['101' ; '110' ; '001' ; '011'];
xn = str2num(x);
dlmwrite('#TEST.txt', xn, 'precision','%03d')
type #TEST.txt

101
110
001
011

You will have to experiment to tweak it to your specifications, but this seems to be as close as dlmwrite can get to doing what you want.

[Lennart]

Hm I actually thought I allready tried that, but apparently I did not. Unfortunately str2num deletes all preseding 0s. So a 011 turns to 11, which is not suitable :(

[Star Strider]

The format descriptor in the 'precision' name-value pair argument puts them back. If you want to write string data, you will have to use fprintf and create your own loop to write the data:

fido = fopen('#TEST.txt', 'wt');
for k1 = 1:size(x,1)-1
    fprintf(fido, '%3s, ', x(k1,:));
end
fprintf(fido, '%3s', x(end,:));
fclose(fido);
type #Test.txt

101, 110, 001, 011

[Lennart]

There we go! It is not %3s because it is 3 bits right? I thought I would have to adjust that number to the number of bits but 3 as well works for values with i.e. 7 bits. Should it be that way?

Do you want to post that answer as a separate answer so I can accept it?

Thank you very much for your help!

[Star Strider]

My pleasure!

Yes. The '%3s' format string guarantees a 3-character-wide text field.

If you want all the entries in your file to have a 7 (or larger character field), change the format string to accommodate it, for example '%7s' for a 7-character field. However, the string has to have the requisite number of leading zeros already in the string for that to display as you want it to. If it does not, the field will still be 7 characters long, but right-justified so the left positions are blank.

The '%3s' will accommodate larger fields, but shorter strings will be out of alignment, of varying length but at least 3 characters long. If you want them all in alignment in your file, use '%7s' (or '%8s' to print entire bytes).