FREAD() help

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Edward
Edward on 4 Apr 2012
Hi so im trying to use fread in a very simple program. Ive used the following to write 4 numbers into a .txt file:
fid=fopen('data.txt','wt');
fprintf(fid,'%0.0f %0.0f %0.0f %0.0f', 2, 4, 6, 8);
fclose(fid);
Now i want to read the data back in by reopening the file and reading into an array:
fid=fopen('data.txt');
numbers=fread(fid);
now if i output 'numbers' i get some completely random numbers:
[ 50 32 52 32 54 32 56]
What am i doing wrong? I should be getting [2 4 6 8] back?
Also if anyone knows why im getting an output 'ans=0' that would be useful too.
Thanks!

Accepted Answer

Jan
Jan on 4 Apr 2012
fprintf writes the data as ASCII strings, so you get the string "2 4 6 8" in the file. The binary representation of this string is:
Str = '2 4 6 8';
double(Str)
>> 50 32 52 32 54 32 56
E.g. char(32) is the space character.
Strings written by fprintf are read by fscanf:
fid = fopen('data.txt');
numbers = fscanf(fid, '%f %f %f %f);
fread is thought for reading data written by fwrite.
See also the help and doc for these 4 commands.

More Answers (1)

Sean de Wolski
Sean de Wolski on 4 Apr 2012
You have to specify the precision of the numbers you're reading (i.e. double).
You could also look at dlmread and dlmwrite if the whole text file will be numbers.
  1 Comment
Edward
Edward on 4 Apr 2012
I've tried changing it to use fread(fid,4,'double'); but still get the same random numbers

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