MATLAB: Fprintf and fscanf same format fail to read file. appreciate help

fscanf formatMATLAB

I wrote a text file (on a windows PC). (A is large matrix of size [29909961, 4] elements)
fid=fopen(filename,'w')
fprintf(fid,'%5i%5i   %17.4E%17.4E\r\n', A);
fclose(fid)
but fscanf fails to read it in again. have tried a bit with different options, but no success
fid=fopen(filename,'r')
K51=fscanf(fid,'%5i%5i   %17.4E%17.4E\r\n');
%K51=fscanf(fid,'%5i%5i%20.4E%17.4E%\r%*c%\n%*c');
fclose(fid)
appreciate the help!

Best Answer

MATLAB is NOT Fortran.
As Stephen notes above and is documented, fscanf returns a single array of a given class; if there are any doubles in the input file, then the output returned has to be double.
What is also documented but you have to read every stinkin' line through to the end to find it is:
"Format specifiers for the reading functions sscanf and fscanf differ from the formats for the writing functions sprintf and fprintf. The reading functions do not support a precision field.
So, the thing that is breaking your input read is the ".4" in the e-format fields in your format string. It simply isn't supported by MATLAB. (I don't know if this true of underlying C fscanf or is only a limitation in the TMW-suppled vectorized versions of MATLAB.)
To read all numeric data you don't need the specific format and are better off without it...just use '%f'
>> x=[randi(100,20,2) rand(20,2)];   % dummy data set
>> fid=fopen('jorgen.dat','w');
>> fprintf(fid,'%5i %5i   %17.4E %17.4E\n', A.');
>> fid=fclose(fid);
>> fid=fopen('jorgen.dat','r');
>> fscanf(fid,'%f',[4,inf]).'
ans =
   36.0000   17.0000    0.1066    0.8530
   84.0000   80.0000    0.9619    0.6221
   59.0000   32.0000    0.0046    0.3509
   55.0000   53.0000    0.7749    0.5132
   92.0000   17.0000    0.8173    0.4018
   29.0000   61.0000    0.8687    0.0760
   76.0000   27.0000    0.0844    0.2399
   76.0000   66.0000    0.3998    0.1233
   39.0000   69.0000    0.2599    0.1839
   57.0000   75.0000    0.8001    0.2399
    8.0000   46.0000    0.4314    0.4173
    6.0000    9.0000    0.9106    0.0497
   54.0000   23.0000    0.1819    0.9027
   78.0000   92.0000    0.2638    0.9448
   94.0000   16.0000    0.1455    0.4909
   13.0000   83.0000    0.1361    0.4893
   57.0000   54.0000    0.8693    0.3377
   47.0000  100.0000    0.5797    0.9001
    2.0000    8.0000    0.5499    0.3693
   34.0000   45.0000    0.1449    0.1112
>> fid=fclose(fid);
>> type jorgen.dat  % to compare
   36   17          1.0665E-01       8.5303E-01
   84   80          9.6190E-01       6.2206E-01
   59   32          4.6342E-03       3.5095E-01
   55   53          7.7491E-01       5.1325E-01
   92   17          8.1730E-01       4.0181E-01
   29   61          8.6869E-01       7.5967E-02
   76   27          8.4436E-02       2.3992E-01
   76   66          3.9978E-01       1.2332E-01
   39   69          2.5987E-01       1.8391E-01
   57   75          8.0007E-01       2.3995E-01
    8   46          4.3141E-01       4.1727E-01
    6    9          9.1065E-01       4.9654E-02
   54   23          1.8185E-01       9.0272E-01
   78   92          2.6380E-01       9.4479E-01
   94   16          1.4554E-01       4.9086E-01
   13   83          1.3607E-01       4.8925E-01
   57   54          8.6929E-01       3.3772E-01
   47  100          5.7970E-01       9.0005E-01
    2    8          5.4986E-01       3.6925E-01
   34   45          1.4495E-01       1.1120E-01
>>
Even simpler is the now sadly deprecated textread --
>> textread('jorgen.dat')
ans =
   36.0000   17.0000    0.1066    0.8530
   84.0000   80.0000    0.9619    0.6221
   59.0000   32.0000    0.0046    0.3509
   55.0000   53.0000    0.7749    0.5132
   92.0000   17.0000    0.8173    0.4018
   29.0000   61.0000    0.8687    0.0760
   76.0000   27.0000    0.0844    0.2399
   76.0000   66.0000    0.3998    0.1233
   39.0000   69.0000    0.2599    0.1839
   57.0000   75.0000    0.8001    0.2399
    8.0000   46.0000    0.4314    0.4173
    6.0000    9.0000    0.9106    0.0497
   54.0000   23.0000    0.1819    0.9027
   78.0000   92.0000    0.2638    0.9448
   94.0000   16.0000    0.1455    0.4909
   13.0000   83.0000    0.1361    0.4893
   57.0000   54.0000    0.8693    0.3377
   47.0000  100.0000    0.5797    0.9001
    2.0000    8.0000    0.5499    0.3693
   34.0000   45.0000    0.1449    0.1112
>>
it saves messing around with file handles and format string entirely for all-numeric data arrays. textscan can do the same excepting have to use file handles and then cast the cell array to double manually.
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