Format Array column in fprintf

Hello everyone,

I have used the command fprintf to write the data in .dat file

but the result give me as

        1  0.000000       0.000000       0.000000
        2  0.000000       0.000000       4.000000
        3  0.000000       0.000000       1.000000
        4  0.000000       0.000000       2.000000
        5  0.000000       11.000000       4.000000
        6  0.000000       12.000000       4.000000
        7  0.000000       13.000000       4.000000
        8  0.000000       14.000000       4.000000
        9  0.000000       15.000000       4.000000
        10  10.000000       16.000000       4.000000
        11  10.000000       17.000000       4.000000
        12  0.000000       18.000000       4.000000
        13  0.000000       12.000000       0.000000
        14  0.000000       11.000000       0.000000
        15  0.000000       10.000000       0.000000     etc.    

How to re-format to get

         1  0.000000       0.000000       0.000000
         2  0.000000       0.000000       4.000000
         3  0.000000       0.000000       1.000000
         4  0.000000       0.000000       2.000000
         5  0.000000       11.00000       4.000000
         6  0.000000       12.00000       4.000000
         7  0.000000       13.00000       4.000000
         8  0.000000       14.00000       4.000000
         9  0.000000       15.00000       4.000000
        10  10.00000       16.00000       4.000000
        11  10.00000       17.00000       4.000000
        12  0.000000       18.00000       4.000000
        13  0.000000       12.00000       0.000000
        14  0.000000       11.00000       0.000000
        15  0.000000       10.00000       0.000000     etc.    

[Sudhakar Shinde]

check formatspec with frpintf.

Answer 1

[Stephen23]

The short answer is: not easily.

Your output example has varying numbers of fractional digits

0.000000 % six decimal places
4.000000 % six decimal places
11.00000 % five decimal places

and also varying numbers of significant digits:

0.000000 % six significant figures
4.000000 % seven significant figures
11.00000 % seven significant figures

This excludes using one simple fprintf command (i.e. based on %f or %g) using only your input matrix.

The long answer: one possible approach is to create an array with the required number of significant figures (or decimal places) for each value and use this with the '*' placeholder syntax, e.g. where M is your matrix:

>> X = 7-(M==0);
>> Y = reshape(permute(cat(3,X,M),[3,2,1]),8,[]);
>> fprintf(' %9d %#9.*g %#15.*g %#15.*g\n',Y(2:end,:))
         1  0.000000        0.000000        0.000000
         2  0.000000        0.000000        4.000000
         3  0.000000        0.000000        1.000000
         4  0.000000        0.000000        2.000000
         5  0.000000        11.00000        4.000000
         6  0.000000        12.00000        4.000000
         7  0.000000        13.00000        4.000000
         8  0.000000        14.00000        4.000000
         9  0.000000        15.00000        4.000000
        10  10.00000        16.00000        4.000000
        11  10.00000        17.00000        4.000000
        12  0.000000        18.00000        4.000000
        13  0.000000        12.00000        0.000000
        14  0.000000        11.00000        0.000000
        15  0.000000        10.00000        0.000000

[Trang Hu Jia]

Hello Stephen Cobeldick

Thank you very much for your help.

I have try with the code that your suggestion.

>> X = 7-(M==0);
>> Y = reshape(permute(cat(3,X,M),[3,2,1]),8,[]);
>> fprintf(' %9d %#9.*g %#15.*g %#15.*g\n',Y(2:end,:))

But the I got the result as

        1   0.00000         0.00000         0.00000
        2   0.00000         0.00000        4.000000
        3   0.00000         0.00000        1.000000
        4   0.00000         0.00000        2.000000
        5   0.00000        11.00000        4.000000
        6   0.00000        12.00000        4.000000
        7   0.00000        13.00000        4.000000
        8   0.00000        14.00000        4.000000
        9   0.00000        15.00000        4.000000
       10   0.00000        16.00000        4.000000
       11   0.00000        17.00000        4.000000
       12   0.00000        18.00000        4.000000

How to fixed it ?

[Stephen23]

"How to fixed it ?"

What MATLAB version are you using?

If you are using Octave then note that it counts significant digits incorrectly for zero:

>> fprintf('%#.3g\n',[0,1,9])
0.00
1.00
9.00

in which case you can simply do this:

>> fprintf(' %9d %#9.7g %#15.7g %#15.7g\n',M.')
         1  0.000000        0.000000        0.000000
         2  0.000000        0.000000        4.000000
         3  0.000000        0.000000        1.000000
         4  0.000000        0.000000        2.000000
         5  0.000000        11.00000        4.000000
         6  0.000000        12.00000        4.000000
         7  0.000000        13.00000        4.000000
         8  0.000000        14.00000        4.000000
         9  0.000000        15.00000        4.000000
        10  0.000000        16.00000        4.000000
        11  0.000000        17.00000        4.000000
        12  0.000000        18.00000        4.000000

[Trang Hu Jia]

Hello Stephen Cobeldick

I got the result already, thank you very much for your help.

This code is very helpful for me

Thanks again!!